I have no clue why people are acting like this would be a bad move for Edmonton. Have you seen their forward depth? Their bottom-6 is just as heinously bad as their goaltending is, and it is way worse than their defense.
Adding Kane pushes one of the Oilers top-6 players into their bottom-6, which drastically helps their depth. If Kane can play like he has in the past, they're also adding a really damn good player. They could run with something like this as their top-9 and have 3 really solid lines:
Hyman-McDavid-Puljujarvi
Kane-Draisaitl-Yamamoto
Foegele-RNH-Kassian
Will this solve all of their issues? Of course not, but it's a big step in the right direction.