Notice how I didn't title this "Buddhism is garbage"; while stupid, Buddhism and its various sects often have nothing to do with what the Buddha actually taught, making them far less attractive as targets for critique. For example, the following were not part of the original teachings of the Buddha, yet are often essential to modern Buddhist practice:
1. Monastic hierarchy
2. Arbitrary rituals and customs (e.g. shaving one's head, wearing a robe, reciting formalized chants)
3. Forbidding sex (obviously in direct opposition to the Buddha's conception of the Middle Path)
4. Reincarnation; "seeing" past lives; dualism
5. Compassion for non-sentient life (e.g. trees and possibly insects)
...and, most importantly:
6. "Isms," or treating ideas as groups to be generalized, "converted" to, etc.
So, fine, the Buddha was right not to incorporate any of these things into his teachings. That's great, but he was nevertheless about as far from being scientifically minded as one can get. Don't believe me? Think the Buddha was some atheist way ahead of his time, or on par with Einstein? Have a look at the following flaws in his modus operandi:
1. The numbered lists: Everything that the Buddha taught seemed to break down into definite lists which more or less could not be challenged by his disciples. Perhaps you think this point ironic, since I'm putting it on a list of my own, but the difference is that I will neither title nor close off this list in an attempt to formalize it or make it dogma; in fact, it's very likely that I'll add onto it in the minutes and hours following my publishing this post.
Given the nature of data and the very states of impermanence and not-self that the Buddha was so fond of demonstrating, he should have more carefully considered that his lists would need updating and refinement as he encountered more worldly problems. Likewise, he should have considered listening to others, and consequently spent equal amounts of time both teaching and learning. Titling your list "The Noble Eightfold Path" or "The Four Noble Truths" is setting you up for adulation and blind acceptance on the part of your "followers." Wouldn't it have been better for the Buddha to have simply said, "I've found four things about reality that are worth teaching, but I, in being imperfect, am both student and teacher, just as you are. If you happen to find a fifth noble truth, by all means, let me know about it"? Certainly, the Noble Eightfold Path is very far from a complete list of methods for avoiding suffering; it doesn't even account for what currently appears to be the primary cause: unregulated emergent process.
2. The neglect of non-human causes of suffering: The Noble Eightfold Path basically asserts that we can end all suffering by changing our thoughts and actions. This is patently false; anyone who has ever passed a kidney stone, been shot in the stomach, or endured cancer can tell you that intense pain, no matter how good you are at managing it, is a by-product of material interactions which cannot be stopped unless their causal processes are. In other words, while I may be able to deal with suffering better upon taking up the Noble Eightfold Path, this in no way demonstrates that my newfound ability to cope with suffering also leads to the cessation of said suffering. It doesn't matter how great you are at meditation, mindfulness, or detachment from desire; if you're being beaten with a baseball bat or ripped apart by an alligator, your psychological sophistication is not going to prevent -- or even mitigate -- your suffering. Incidentally, how meditation could ever help starving baby birds is beyond me.
The solution really is far simpler than a contrived set of mental practices requiring extensive training: Just don't have kids.
3. The ambiguity: The Buddha often spoke in parables and metaphors -- which, in the general sense, may occasionally edify a person seeking to understand an elusive concept not easily grasped using more literal means -- but the Buddha is almost never direct with his followers in the Pali Canon. The lack of clarity of wording has had such dramatic consequences, in fact, that today, there are entire "Buddhist" sects which teach literal reincarnation where the Buddha only ever spoke of a metaphorical "rebirth" of one's moral energy, or kamma. Worse still, the concept of rebirth isn't even all that accurate: One transfers one's ideas, notions, and physical actions through the world both while alive and after death, so it's a continuous process, and not something that occurs exclusively after the body ceases to function. Counter by claiming that, in accordance with the flux of material reality, the Buddha was referring to the continuous generation of new "selves" who have causal influence on their environments and you'll further illustrate my point that the wording of the Buddhist texts is so ambiguous that we can't even agree on what it's referencing.
This problem could have been easily solved by the Buddha's referring to the phenomenon in question as simple transmigration of data and information -- both physical and conceptual -- rather than as a "rebirth."
4. The gods: Contrary to popular belief, the early Buddhist texts are filled with nonsense about gods of all sorts. Dimensions, planes, and immaterial consciousnesses are often spoken about as things which the Buddha confronts during intense meditation sessions. Essentially, they're all leftovers from the obviously whacky Hinduism, but the Buddha took what were integral facets of a supreme godhead and turned them into imperfect, desirous beings capable of suffering just like anyone else. The claim that a conscious, sentient being is necessarily imperfect, in part because of its desires and impetuses, is accurate; the claim that any such beings exist beyond the Earth, or in other realms of existence, has no basis in empirical observation whatsoever.
It's like saying that, even though it's quite obvious that man contrived Santa Claus, there could be a guy who rides a sleigh driven by flying reindeer somewhere in another dimension -- except that the Buddha apparently took the unfounded presumptions of his backward Indian culture quite seriously, to the point where he actively believed that gods and ethereal realms were real in the most literal sense imaginable.
5. No suicide or antinatalism: If ending suffering is the most important activity of life, then why didn't the Buddha advocate suicide or the cessation of human reproduction? You can counter by claiming that spreading the word on how to obtain enlightenment is a far better use of one's time than suicide, given that it will help end not just your own suffering but the suffering of others, but what if you're suffering so horribly that meditation does nothing to ease your mind? Is it okay to kill yourself? Furthermore, even if there were a valid reason within the Buddhist paradigm to forbid suicide, what does that have to do with merely refraining from having children? Sure, modern monks don't reproduce, but that has more to do with the false notion that the Buddha advocated abstinence than with any desire to end life as we know it -- and, assuredly, monks do not attempt to stop laymen from reproducing.
It seems rather obvious to me that the Buddha was entirely invested in the agenda of life: He saw that part of it was bad, but instead of trying to fix it proactively, he advocated messy self-help steps for those unfortunate enough to have had to endure the onset. If he'd truly been interested in eliminating all negative sensation, he'd have said more on how to cleanly terminate one's own life -- or at least strongly emphasized the importance of abstaining from sexual reproduction (regardless of social status).
And above all else, no matter what the Buddha actually said, the fact that some 350 million people continue to not only venerate but outright deify him goes to show what a mess we're in. If I, a random, anonymous person on the Internet can so effectively dissolve the original words of the Buddha with a few paragraphs, then why is he being treated with such reverence? Why is he being singled out above billions upon billions of people? If I can put a dent in his ideas, and there are seven billion people on Earth, how many others do you think can do the same?
Is it possible that the entire "path" advocated by the Buddha is -- like just about everything else that justifies enslavement to non-rational cognitive faculties -- a sham? Here's a final word of advice: No matter how much you agree with a person or set of ideas, if the method used to arrive at those ideas is flawed, or if the ideas share space with really stupid ones, you're better off not trying to gain social status through associating with their "isms." Always discuss ideas one at a time.