Why did you think the arc dragged? Iirc the battle itself only lasted a little less than a dozen chapters, which isn't any longer or shorter than the other action-packed arcs of the manga. I wouldn't call the end of RtS a full on shitshow either, even if I disliked the idea of the serumbowl. Its execution wasn't half as bad as what most anons make it out to be imo, and the basement reveal that came afterwards was well worth the wait.
As for Erwin, I agree that the very fact that he feels guilt over his selfish desire makes him a much better person than what he sees himself as, but I didn't think his final stand felt particularly dumb, mostly because his selfishness was already hinted at in Uprising (namely in chapter 51 and with his convo with Zackley) before being properly explored in RtS. I also thought his actual death was a pretty neat reference to Moses and his being forbidden to enter the promised land for the one sin he committed despite being one of God's most faithful servants. I don't know how intentional that was, though.