First encounter with the Emperor has been criticised before on this forum - it forces a narrative outcome, which feels odd especially that later, after aquiring the hammer, players CAN resist the Emperor. So why not add some content, and make this choice available earlier? Well, I think it is because otherwise we wouldn't have a need for hammer - or if we were able to disobey the Emperor, but than were forced to free the Gith that would greatly gimp our interactions with Raphael.
Oh I am sure there could be a major redesign to fix that narrative problem, but it would require either some major restructuring of Act3, or completely change Raphaels deal. On a side note, I wonder how much of act3 was planned when they were making act1. Whenever it is true or not, to me it feels like they make making stuff up as they go along, rather than the story being revealed overtime.
So it seems to me that Larian is struggling with tying up all the threads that they have set up, rather than not finishing the game. Maybe they had a grand plan initially, which became unfeasible after they better realised the scope of their game. Maybe they could have done smarter cuts if they haven't revealed so many plot threads in EA which were: 1) already polished to a pretty high standard and scrapping them would mean scrapping content in a pretty advanced stage of development 2) Players would see it and probably would be more upset that something was removed from first 40h of gameplay, than if they would underdeliver a narrative payoff in 140thh of gameplay
Ending is that I will give you felt like something was missing, but I also think that if you are not going to ship with something, than the epilogue is not a bad thing to ship without. For one, a big chunk of your player base will not see it in time (or ever). and for those that do finish the game, reloading a save later and seeing a better conclusion for your adventures works just fine.
Except that this is Larians own doing. The Emperor was inserted into the story very late in development which required massive rewrites. And the effects of those rewrites are seen all over the game, from the messy narrative to vestige of the old story that make 0 sense.
All of this is Larians fault and not an excuse for the bad state BG3 is in. The reason they did not have a grand plan is that they scrapped their plan a few months before release and decided to simplify everything and remove as much consequences and choices as possible.