I still maintain his striking is something special and was years ahead. But that Aldo fight (his big impress at the top) is almost 4 years old now.
Nate was bigger than Conor and weight classes exist for a reason. Conor hits hard for his size... but not for someone comfortable a couple weight classes up. Conor landed over and over and just couldn't starch the fighter used to bigger shots.
Whatever skill gain there was going to be at this point would have happened. 4 years at the top and we haven't seen the ground or even ground defense come with it, let alone the interest in staying active. So much damn potential. At the top for that fleeting moment.
As for Khabib, he smashes everyone, so it's not like Khabib exposed a lack of ground game on his own. But we have never seen anything new. All the great strikers that managed to get a nod at best of all time had to show some ground defense during their run.
Like you said, managed better and it feels like some very small additions and a straight head could have kept the machine going.