He used to talk like an old timey boxer using wit and humor to charm an audience.
Fast forward to now: I think the cocaine use has made it impossible for him to speak like that again. He's just angry and screaming most of the times these days.
Think of it this way. If the Conor of 2015 were to say what the Conor of 2021 says, with his banshee screaming and blunt rage, no wit.... He wouldn't be popular.
Fighting skill set aside. Even if he was winning fights, but was rage screaming like he does now, he would have never been popular in the first place. 2015 Conor grew to fame because of slick wit. He doesn't possess that anymore.