Honest question. Did you watch Jagr and his teams in from about 1995 onwards?
Apart from Mario coming back in 2001, he was mostly carrying cast-offs, misfits and projects.
His one good side kick was Straka (both in Pittsburgh and in NY), the KLS line was a thing for a couple of years, while Jagr played with Jan Hrdina, German Titov and the corpse of Kevin Stevens, etc.
The defense during the Pens years was mostly a flashy but inconsistent Darius Kasparaitis, and such household names as Jiri Slegr, Ian Moran, Andrew Ference, etc.
The NY years were even more ridiculous, he carried a franchise that was a laughing stock back into relevance - all accompanied by, again, misfits and cast-offs, Nylander, Straka, Rozsival, Rucinsky, Malik, etc.
Lundqvist came up, some rookies like Tyutin and Girardi, etc.... But make no mistake about it, it was a hell of a carry job by Jagr.
Also, Jagr won 5 Ross trophies, not 3. Why are you just counting 3? (other than to better suit your agenda)
Jagr was so far ahead of his competition that he could miss 20 games and still win the Art Ross, ahead of players like Bure, Forsberg, Fedorov, Sakic, Lindros, etc.
(and that actually happened in 1999-2000, played 66 games and won the Art Ross).