Because the hit rate for sitcoms is infinitesimal, and it's still cheaper to buy Friends than it is to commission two hundred new shows 199 of which sink without trace.
The Office and Parks and Rec struck creative gold under strict network constraints. Easy to produce, affordable ensemble cast, relatable content. Then, as they found their footing, they could expand upon this soulful base and have more elaborate sets, celebrity guests, broad plot arcs, etc.
By contrast, Netflix shows are unconstrained, working from the other end. They are trying to spend endless money to emulate these predecessor shows in the late stage when they were massively successful, rather than when they were uncertain and fledgling.
I think Space Force is a good example of this. All the right pieces to make a hugely successful show, high budget VFX, setpieces etc, but no soul.
Netflix IMO tries to make shows that are very zeitgeist-y, instead of evergreen, like Friends and The Office. I think that will come back to bite them in the future because I don't see anybody wanting to license one-offs like Tiger King or Squid Game for syndication down the line.
Meanwhile, decades-old shows like Law and Order, Frasier and Two and a Half Men are still making bank because they have tons of episodes and are generalist enough to be popular across pretty much any cable network globally.