Why isn't he a "winner" though? iirc he showed up big time in some nba finals games and won a championship.
How do you define a winner? Would you not want cp3 cause he isn't a winner and can't get to the finals? Would you not want Anthony Davis cause he isn't a winner and can't make the playoffs? Paul pierce wasn't a winner until ray Allen and garnett showed up right. Those two (garnett and allen) weren't winners until they joined Paul pierce.
He is statically one of the worst defenders ever. He is a player that relies on over dribbling to take tough contested shots, which stalls out the offense.
He is a perfect player next to Lebron because Lebron can carry him to the Finals then Lebron can hope that high variance of Kyrie's possible performances trends up for a series where they are outmatched talent wise.
If you are night in and night out relying on Irving to carry you, the variance in his outcomes is too inconsistent as a first option, especially since he is a huge negative on defense and doesnt move the ball enough to make anyone else better on offense.