Yeah, that’s why I specified Kucherov’s prime. He took a few years to reach his ultimate level - probably because he had to develop that insane intuition and ability to read the play, while McDavid came into the league a ridiculous natural athlete.
Again though, Kucherov missed a season and a half in his prime due to injuries, and in the half season he played he was barely behind McDavid’s scoring pace. So you already have him outscoring McDavid in two seasons, as well as leading him in a third before being passed at the very end; if Kuch had stayed healthy those two prime seasons and at least been competitive with McDavid (which almost certainly would have been the case), possibly even beating him in one of them (speculative, but certainly not outside the realm of possibility), it’s difficult to see how you don’t put them on the same tier.
Let’s look at it season by season, starting at the point Kucherov hit his prime (as unlike McDavid who came into the league a physical beast, Kuch needed a few years of exponential growth before reaching his ultimate level):
2017-18: McD 108, Kuch 100. Kucherov was leading before letting off the gas and getting passed at the end of the season. Clearly they were competitive this year.
2018-19: Kuch 128, McD 116. A clear win for Kucherov, who put up what was at that time the highest-scoring season since Lemieux in ‘95-96.
2019-20: McD 97, Kuch 85. A clear win for McDavid, who followed a 12-point loss to Kucherov with a 12-point win over him in a shortened season.
2020-21: Kucherov missed the entire season due to injury. McDavid went beast mode this year so Kucherov certainly would have had his work cut out for him, but considering the incredible postseason Kuch put up while playing through multiple injuries I don’t think we can rule it out. Still, it’s a no-contest between them.
2021-22: Kucherov missed almost half the season due to injury. McDavid scored 123, while Kucherov in the games he did play was pacing for 120. Again, we’ll never know what would have happened had Kuch been able to stay healthy, but clearly he was playing on the same level as McDavid this season.
2022-23: McD 153, Kuch 113. A dominant win for McDavid, who topped Kucherov’s previous total by putting up the new highest-scoring season since Lemieux’s ‘95-96 campaign.
2023-24: Kuch 144, McD 132. A clear win for Kucherov, who once again bests McDavid by 12 points.
So from the time Kucherov hit his stride he’s beaten McDavid’s scoring by double digits twice, been beaten by double digits twice, and been on the same level twice, with one season being missed entirely.
That being the case, I don’t see how you don’t put the two of them on the same tier. You can fairly argue that McDavid has the edge in the regular season as he peaked a little higher, hit his stride sooner upon entering the league, and has stayed healthier, but then Kucherov has been the most dominant postseason player of his generation and one of the greatest of all time. Regardless of how you rank the two, there’s no way the gap between them is large enough to put one of them on a lower tier than the other.