Quoting: BCAPP
Just like people who say Crosby did. When he had a higher cap percentage than other stars and had a deal that would be illegal today artificially suppressing his cap hit with 3 years of 3 mil at the end. Every year before that is above his 8.7
There may be more of argument to the Crosby deal since he was already a star and probably could have asked for even more despite getting a lot of money. Same with McDavid for that matter, what were the Oilers going to do if he said he wanted a $16m AAV or w/e the max contract was when he signed his deal? They're certainly not going to say no so he did take less money.
MacKinnon hadn't established himself as a franchise player yet and was coming off of a 52 point in 72 game season so he was still a bit of a question mark for what his ceiling actually was. I get what you're saying, but not really the same situation.