1. Unlimited tactics - get them here or chesstempo for free.
2. Lessons - That don't help you improve
3. Videos - This is a good feature but they only allow it for diamond members.
4. Access to databases that you get for free on other sites.
My main problem with chess.com is their tier system of membership. Even if you support the site financially they still restrict your use depending on your membership level. A gold member for example is limited to 25 tactics a day. A platinum member gets unlimited but only 10 lessons a day and no access to videos. The biggest scam though is limiting game analysis. Something that costs chess.com nothing as they use Stockfish.
Any mention of lichess on their site gets deleted immediately. Apparently Eric says mention of the site is ok but comparisons are not allowed. The mods have clearly not got that memo.
I was a diamond member for months. I wish I had found this site sooner. I can't donate too much a month to this site just now but when I can I will definitely be paying more.