I kind of missed the part of commanding the summon to do something (despite the button bloat if you spammed a lot of pet actions.) during it's auto-attacks instead of seeing them idle and sacrifice themselves from existence.
But one thing I appreciate with the 6.0 or to be more specific the 6.1 iteration is:
(6.0 and before) Carbuncle daydreaming "C-Carby wake up it's time to cast your devotion.!" fails to do it before Phoenix/Bahamut.
(6.1):"I'll do it myself! (Searing Light)"
Another thing in 6.0 that got removed was the ability to instant cast most of the Lost actions with Dreadwyrm/Firebird trance.
Though I mainly used to play both SMN and MCH in 5.0, nowadays I pretty much play MCH with SCH instead of SMN for its small reminiscent of me playing 5.0 SMN.
As for 4.0 Machinist I didn't get to experience that one that much as I was on the rush leveling it from 61 to 70 in HoH when the maintenance for Shadowbringers was about to happen. (The Automaton Queen from the job trailer pulled me over to play it.)
(4.0) Sprout Day me: "EMERALD YEET HIM TO THE WALL!!"