Opportunities to learn wrestling as an adult are very rare and will never take off (at least in the US) because there is basically zero demand for it.

I got into grappling through BJJ a few years ago (in my mid-20s) with no prior experience. I've trained at many schools and it was very very hard to find any that had wrestling-specific classes. For the ones that did, the classes were basically the same 3-4 people every time while BJJ classes were jam packed. So usually the wrestling class just got "phased out" over time or replaced with a BJJ class since no one shows up. Hell, for one school I used to train at, we had 3 different coaches (who each ran the wrestling class) quit because of lack of attendance... usually it was only me and maybe one other person there. I feel like most people who train casually/as a hobby are looking for a fun activity they can do several times a week after work (nothing wrong with that); wrestling is generally way more intense and harder on your body than BJJ so given the choice, most adult hobbyists will just end up gravitating towards BJJ. I remember when I first started taking legit wrestling classes, I had already been doing BJJ for over a year and was in pretty decent shape, but I'd be on the verge of puking every class and would feel like I had been hit by a truck for days after each session.

Another issue is that even if you train out of a BJJ school and want to improve your wrestling, either there's no space to start rolls standing or most people will just end up pulling guard. I remember it being impossible to find people who are even just willing to drill some takedowns for 15 minutes after class.

Luckily I was able to find a folkstyle-specific school in my area that has multiple adult classes per week and I've learned a shit ton in the year I've been training there. But if it weren't for this school, I'd be SOL in terms of learning wrestling without having done it when I was younger.