The goal is to win playoff series until you win the cup, which Mack also does better than Matthews.
Let's compare apples to apples.
Matthews at age 19 (2016-17) scored 40 goals 69 points in 82 games
Mackinnon at age 19 (2015-15) scored 14 goals 38 points in 64 games
Matthews at age 20 (2017-18) scored 34 goals 63 points in 62 games
Mackinnon at age 20 (2015-16) scored 21 goals 52 points in 72 games
Matthews at age 21 (2018-19) scored 37 goals 73 points in 68 games
Mackinnon at age 21 (2016-17) scored 16 goals 53 points in 82 games
Over his 19 - 21 years Matthews scored 111 goals 205 points in 212 games
Over his 19 - 21 years Mackinnon scored 51 goals 143 points in 218 games
I agree with you that there is a
large difference between these two players.