I don't think it's fair to just say "well the Rangers are good, so leading them in scoring is an accomplishment." The Rangers are objectively not good at scoring even strength goals.
The expectations are different for a player like Kreider. For Panarin's ability, leading the team in scoring is bare minimum. He should be one of the league leaders. I don't think that's unfair.
You can say "well, it's just because of salary" and yes, salary sets expectations. Again, I don't see anything unfair there. At $11.6m you're paying for a guy near the top of the league, not at the top of team.