your ISP just sees what sites you connect to, but not what you do
it'd be like
connected to steam
connected to google
connected to discord
not
Signed into steam (Username: BobMcJoe Password: imgay), talked to friend about gay stuff
searched for "gay discord servers"
joined the "traps are hot" discord server (username: Joebob password: thegayest)
(Unless it's HTTP and not HTTPS.)
Still, just because they can won't mean they will. Plus, you can set up a VPN on another network with other people or pay for a subscription to one, and they'll have a lot of data and won't know whose it is.
Plus, nobody's going to care what sites an individual visits. It's pretty unlikely that they won't strip your info from it, they'll probably just provide general tags about your age and race and stuff at worst.
so basically nothing's wrong and if you use a VPN they won't have anything other than "connected to VPN a ton" to sell.