I've identified as a feminist since I was about 12, however I wouldn't say I fully understand it until a lot later. However I very much understood the basic principle, who could not?
I was on the boys football team in primary school, it made the local paper (!), it was almost unheard of back then, at least where I lived. The school had no issue with it, to their credit. A lot would have. I did not come from the most forward thinking of areas.
Maybe the women you spent time with aren't feminists?
The waist trainer thing concerns me, it sounds like it could be harmful, and it definitely isn't a concept that is OK.
The thing that disturbs me the most is the reason behind the choices - "well, men like big ones". To me your health, outwards appearance - that should be for you! Don't alter your body to the preferences of someone else.
I agree the pressure on young people is insane in different ways today than it used to be. The media have a lot to answer for on this issue. I grew up in the 80s and 90s and while it wasn't perfect, I honestly believe it was a lot better overall. No social media (while I accept there is a lot of good that has come through social media, I have huge concerns regarding how children and teenagers use it and are affected by it - the constant messages regarding so many things).
Maybe you just ran into a group of women who are interested in appearance and men, not everyone is like that. But yes there's a massive focus on appearance now. People having cosmetic surgery at 18. Lip fillers. Spending 4 hours on make-up. Make-up that changes the way you look to an extreme extent (have a look on youtube! some of it is fascinating to be fair). I wonder how a girl who wore no make up and had long natural hair would be treated in high school and outside of school now? Would it be OK?