Apart from being able to play, you can also learn how to play chess, watch others play and tackle chess puzzles.
In terms of content however, there’s little to complain about. While there’s nothing wrong with that, it can take a while to get a good handle on where everything is. It doesn’t have much in the way of aesthetics, unless you’re really into minimalism. That sounds like the perfect service, but you should know that the site is also very barebones. Lichess has no advertising, no requirements to pay anything, and offers the ability to both learn and play chess.
Paying a subscription simply removes them, but there are no other advantages we can see.