I wonder if significantly shorter term was ever on the table. Something like 3 years and 12 million. Or 2 years, try your hardest to win a cup and leave for greener pastures once Makar gets his raise and the cap has confirmedly risen.
The long terms seems what screws over things -- both sides, even, which was evident in Mack's 2nd contract @ $6,3M per and seven years. I get that it's security but career ending injuries are still rare and even with a, say, three year bridge deal Mack would've gotten almost 20M in addiction to his ELC millions. I think a lot of the Avs contract controversy stems from the fact that Mack played many years as the most underpaid player in the league. Had he gotten more money earlier perhaps suddenly it's not as crazy to let Rantanen have his due, too.
Although if it's really about depth and not willing to be as dumb as the Leafs front office then I get it and you just have to respect their decision.