I’ve heard that high level D&D sucks ever since I got into D&D back in 2e, so I don’t know if 5e truly sucks, or it’s just continued player sentiment toward something that’s always been, IMO, misunderstood.
Personally, I fucking love epic level shit. Starting at 20 and using the epic level book to go further is awesome. The problem I see, though, is DMs quite often don’t think epic enough. They think too small scale and it sucks for everyone because
There’s a lot to keep track of on a single character. So many spells and abilities at that point, and if you’ve never really played a lot of high level stuff, you can get choice paralysis or just not know how some of your stuff really works.
Strength. What’s a challenge? Quite often when I see what others are using in their high level campaigns, they are just poorly balanced large scale battles or a single big monster and not really thought out. If your party has close to God like powers, they should be fighting actual gods.