Well, that's the rub, isn't it? If you go in with expectations that it's at all going to match the insanity of the Infinity War Saga, you're probably going to be disappointed no matter what. Who had expectations for Infinity War going into Iron Man 1? Not a single person, except that one guy somewhere who's got a wall of Marvel products from the 80s who finally got it right after 30 years of waiting.
A lot of my friends are doing that same thing and I am begging them to let go of expectations and be accepting of something new. None of the original Avengers remain by the end of Endgame: Tony Stark and Black Widow are dead, Steve Rogers is an old fart who passed the Captain America torch to someone new, Bruce Banner has apparently permanently lost the use of one of his arms which although not discounting Hulk entirely severely cripples him, and Hawkeye-turned-Ronin is... a family guy now? He's always been the Meg of the Avengers anyway with his dorky arrows.
I'm ready for a new 'big' story if they want to work up to that, and I'd prefer if they not try to match the epic insanity of the Infinity War/Thanos story. If they can organically latch onto ideas and deals and certain story beats that resonate with the audience over years and then steer it in that direction like they did with Infinity War, they might be able to pull it off, but even if they stick with something of a smaller scale, as long as they pull it off with as much gusto as they've done with almost all of the films to date, it'll be a good time. I just hope they don't try to shoehorn in a 'new Tony Stark' etc. for the new universe, which would be kind of lazy. Let Shuri and maybe still Banner latch onto the super heady science stuff, but Shuri doesn't have to be an almost omnipotent flying combat billionaire playboy philanthropist on top of it.
Plus, not everyone from the first 3 phases is gone, plenty of them are sticking around, so there's a lot of connective tissue still there between the first epic saga and what's coming next. Stay optimistic!