- Clickies are the worst type of switch.
First off, I see that you've very recently joined. I don't watch the New Members posts as aggressively as I had been able to in the past. Welcome to our eclectic and eccentric band of lunatics.

I would say that's probably the most popular opinion. People seem to tend to write off clickies entirely before they've ever tried any good ones ... unfortunately. I was weird and actually liked MX blue (people make mistakes), but it isn't like much besides MX red in that family is common enough to appeal to the senseless masses anyway as an alternative. MX clear and black are too niche, MX brown is ... well ... MX brown.
The fact that I was once a mutant space alien who actually liked MX blue is probably all that allowed me an open enough mind to go down the wonderful rabbit hole of niche and/or vintage clicky mechanisms ... many of which are simply fantastic. Unequaled, in my opinion ... and I'm pretty sure that is the minority opinion in places outside of Deskthority.
MX clickies, having now had a more rounded/broader experience, are pretty objectively bad. I wouldn't put them below the worst MX tactiles ... but not far behind. If you haven't tried any good alternative mechanisms, however, you don't really have a leg to stand on in making that statement.
- Cheap Tai Hao Caps are better value than most GMK sets
Everything is a better value than GMK, in my opinion.

That may actually be unpopular though.
- Getting into customs is way too difficult for most people, and getting into vintage keyboards is almost indecipherable.
What do you consider to be custom? Custom can be as simple as getting some garbage MX (or clone) board on Ebay for $20 and making it your own. You can pick up a brand new Magicforce 68 for $30 pretty commonly right now. If you're handy with a soldering iron, it is pretty easy to swap in whatever you would like to use in it. I can attest to the surprisingly high quality of the pads/vias for the price. Police surplus TG3 keyboards can be had for dirt cheap with MX blacks as well if you keep an eye out, and those are tanks.
If soldering is what you mean by difficult, there are plenty of affordable hot swap boards, even if you're dealing with cheapie Amazon Outemu (Gaote) hot swap boards that only accept Outemu-ish switches.
This hobby isn't all about drooling over the most popular $300+ GB, etc. The switches are what really matter ... and some of the best ones around are dirt cheap, ironically.
What do you need deciphered about vintage boards? I'm not Chyros (who you should binge watch if you want to go down that rabbit hole), but I have a pretty good understanding of most of the highlights, and experience with a good number of the ye olde forgotten switch mechanisms.
- Garish colors have no place on a keyboard, nor does RGB
I think that both of these are relatively popular opinions, although that matter certainly isn't settled one way or the other. I agree myself, but aesthetics are totally subjective. ¯\_(ツ)_/¯ I'm not looking at the board while I'm typing on it anyway.