Just saw the news myself. I liked the site, so this has pissed me off.
I've never used it before, but an alternative being recommended is
https://hianime.to
Looks pretty similar and seems good so far. Works just the same.
Remember you can export your watch list from Aniwave and import it to other sites. (You can still access
https://aniwave.to/user/watch-list for the time being). It looks like you can only import from MyAnimeList on hianime however, so you'd need to have an account there first and import your Aniwave list.