Well seal clubbing is pretty bad for one. But the point isn't whenever there are bad traditions, but whenever tradition is a good or bad reason to do something. Rites themselves do nothing, burying or burning the body does. Understanding why you're doing something is vastly better than doing it because of some (possibly reasonable but unknown) ancient reason no one is able to point out. Taboo of incest is less related to traditions, and more to biology which causes people not to be attracted to their siblings in most cases. There is no ceremony or ritual to prohibition of incest, so I'd say it's not a tradition. The tradition that have existed, however, was inbreeding of royal families, that wanted to keep their blood pure, which led to copious amount of incest and genetic defects. Many traditions rose from the dominance of one group over another and existed to legitimize this dominance further. Tradition of women being unable to vote, earn money or chose their spouse was born from the many generations of oppression. Tradition of black people being segregated away from white in USA was born out of dehumanization of slaves. There are many cases of traditional honor suicides (like seppuku) or honor killing (like stoning of women accused of adultery) in different traditions as well.

I could keep listing "bad traditions with bad reasons" but that's not the point I've originally made, more of a reply to your point about traditions being born out of useful or natural/survival reasons, which I believe those examples should disprove. The point is still that doing something solely because of tradition is bad, you need knowledge to do that well and in current age there is absolutely no reason not to seek that knowledge. In the past, when people were illiterate an easily digestible oral tradition was useful thing, but we're way past times when we have no good way to ensure the complicated reasons for doing things are preserved. What if some tradition results in oppression of some people and it's source is unknown or so ancient it's no longer applicable, should it be upkept? Conversely, should the ritual blood sacrifice be kept in the celebration of plentiful harvest to appease the gods, or should you only keep the parts like dancing around the bonfire and socializing, because those things are fun and healthy for the community?

If there is wisdom hidden in the tradition, then you want to figure it out, but if it's kept cryptic, unknown and attempts to research it are met with disdain because someone tries to compromise your tradition, then it's probably better to fuck around and find out what would happen if you didn't perform the tradition. And if something bad happens, then at least you can write it down and pass to the next generation as the actual reason for doing things. I seriously doubt there is anything left in human traditions that was figured out in the past, and is currently impossible to decipher or comprehend just by analysis, without even doing empirical tests. And if for some reason something isn't, then do those tests and find out. If you're worried about some arcane knowledge of the ancients that is too enigmatic for us to understand just by looking, you can try doing something differently in isolated environment, with various precautions and on limited sample. No reason to keep it as "tradition" instead of "reason", especially since the underlying reason could have been good, but due to no one knowing what it was, the method could have degenerated over the generations to the point of being ineffective.

So in the cases where I burn corpses, and wear a condom while fucking my sister, wouldn't it be better if my reasons were to stop disease and genetic defect?

If someone asked why I was wearing a condom I could say "so she doesn't get pregnant, also, you want in on this Dad?", and that's better than "because"