No doubt it's an issue, not having top tier coaching and sparring to push your limits and help you improve your game is how great fighters stagnate. Problem is even when Conor was on his way up he openly campaigned about fighting anywhere from 145-170 and literally everyone in that weight range wanted to bash his head in for his shit talk quick rise to fame and promotional push due to his starpower. It's hard to bring guys in who wanna help you improve when you're the money fight EVERYONE wants. Hard to find allies when there's a lucrative target on your back.
Also we see how Conor disrespects his sparring partners lol like when Paulie Malinaggi offered to step in before the floyd fight and help fine tune McG's boxing all Conor did was beat up an old shot fighter than make fun of him on the internet over it lmao. Shit's not conducive to finding quality help, and say what you will about Paulie but the man knows his boxing and woulda been a big help but McG wasn't trying to hear it.