Andy Griffith, MASH, Everybody Loves Raymond, Hogans Heroes, two and a half men, and Big Bang, are all still on every day and still great. I also like Young Sheldon although it has about run it’s course.
Never seen Sheldon and I never got the Two and a Half Men thing, but the rest of your list is solid. I would add All in the Family to the classics that I can always watch.
Traditional network comedies: I can and do watch The Office, Seinfeld, and Parks & Rec repeatedly. Others I've enjoyed in recent times would include Scrubs, 30 Rock, Cougartown, Brooklyn 99 and Happy Endings.
Cable shows I wish were still being made: Silicon Valley, Party Down, The League.
All of these are former shows, so I guess to the OP's original point, I'm not watching or don't know about any great 30 minute sitcoms currently being produced.