I've only been buying/selling on CL's bike section for the past few years but it seems to be the same as it was when I first started. There are a few extra flippers around though and their ads are incredibly annoying - I block them as I see em if there are too many. When it comes to nice vintage bikes in my size, there wasn't much then & that's still how it is now...

I haven't had any issues when buying, and the same goes for selling. All bikes have gone within 1-2 weeks at most. I haven't had an issue with scammers for quite a while either.

I haven't sold or bought a bike through FB but I see it's pretty active over there as well, at least in the listings. Not nearly as much as CL though. I have sold a lot of kids items through FB though. The FB marketplace/groups are huge and there is always a lot of interest, but it can be a huge headache at times. I barely use FB anymore, in general, and have since gone back to CL. It's just easier.

I don't like offerUp and LetGo either. Mainly because of the layouts.