if you've killed Mindflayers (CR 7), Archdruids (CR 12 when NPC), Red Dragons (CR 10 when Young and CR 17 when Adult) at level 4 what's there to really accomplish?
Kill level 8 Mindflayers, Archdruids, Red Dragons. Then level 12 in the last chapter.
Sad thing is, it doesn't matter of the game looses appeal. Beginning is explosive and fast paced, it will look good on streams and people will jump in. Most players don't finish (or get that deep really) games anyway. Play for a few hours, give glowing reviews and move on.
Watching videos that's what struck me the most - how big and loud everything is from the get go. And that unfortunately can get dull rather quickly. At least for me.