The difference between .17 and .18 is pretty substantial. Lemmy.world neglected to update to .18 because captcha support was not working for new account signups, so they waited for v0.18.1
https://join-lemmy.org/news/2023-06-23_-_Lemmy_Release_v0.18.0
There should be substantial performance improvements because it moves Lemmy from using websocket to HTTP API.
There are lots of other fixes and things, but that is the most substantial change.
I have supported Discord with a nitro subscription for as long as I’ve had an account. It’s a terrific program and there’s no reason to expect premium features for nothing in return. The mentality that everything should be free is why we have so many fucking ad driven online business models and I’m over it. I pay for what I use if it’s a good service.