“or even think learning history is worthwhile”
What happened to mesorah? It begins and ends in the last 100 years?
Although you claim so, it’s not so clear from your wording that you just wanted to ‘prove halacha can change’, they’ve been tirades against modern day psak. Nobody disagrees that certain halachos are based on the mitzyus that exists in x community at y time. That wasn’t your point – and if it was, you probably wouldn’t have so much objection.
Your began by saying, “Minhagim once done by only the pious few are now mainstream Halacha”. Then you gave examples that by and large display ignorance if you’re claiming they were once simply minhagim.
Have you learned the sugyas regarding bugs? Have you learned it l’halacha? Do you understand that the dinim, whether “paskened” by rishonim or acharonim must be followed in later generations based on what kind of mitzyus is known? Ok, so there’s a “mutar b’dieved” matzav because their nosen ta’am lifgam – but to have the audacity to claim it’s “minhag” that became “mainstream halacha” simply displays that you have a tremendous lack of knowledge in many of the areas you mentioned.
Perhaps you were just lazy in your writing, but post after post, it seems like you claimed that a whole bunch of minhagim and chumras suddenly became mainstream halacha. A chumra for one generation can absolutely be mainstream halacha for another – especially if the reality changes (i.e. fraternizing at weddings which is osur became much more of a problem in the US as weddings got bigger). Why wasn’t it a problem in Europe? You barely had more than the two *immediate* families. Grandparents – yes, MAYBE some aunts/uncles/cousins (often times not), and a few close friends. Generally speaking, there weren’t problems with fraternizing, now there are. Regardless of the mitzyus, the issue is one of basic halacha being followed.
Beards? I see your problem, I just wouldn’t be bothered by it. So the status quo in Lita was that bochurim wouldn’t have beards, now some bochurim do. I don’t think it’s a result of anything in particular. It’s true that you find more people wearing frocks than once did (newly married avreichim, and even bochurim are raised up with frocks). I don’t really understand it, but I simply wouldn’t be bothered to think too much about it; there is little to do with halacha in that realm (I say little because maybe they wear it to be in line with Hilchos Yom Tov that begodim must be better for YT than Shabbos).