Games played is certainly an important factor to account for because it represents a difference in opportunity to put up a raw point total. The issue is, that's not the only factor that can significantly impact raw point totals, and while some Leaf fans may not like it, those factors are not ignored in real world negotiations. Rantanen is a good player, but his point totals are a bit of a mirage relative to Marner, because he has been a massive beneficiary of one of the biggest impacting factors - PP time, which Marner has been comparatively starved of relative to his historical and current peers.
Remember how we used pace with games played to create a more accurate comparison between two players with differing opportunity? We can do the same thing here with time on ice impacts, and see that Marner was producing at a level in 2018-2019 that, given Rantanen's ES and PP time on ice, would be about 110 points. Rantanen was producing at a 96 point pace. Marner's primary point production was insane that year as well.
It's quite odd that people will so quickly and without thought accept the impacts of games played discrepancies, but there is such massive pushback when acknowledging the impacts of time on ice discrepancies, even though it provides a much clearer picture.