So I've kinda spun back around to my initial stance on it. I think Edmonton needs a new system, and I think the new coaching staff is going to need to demand McDavid make some alterations to his game to find post season success.
Not sure that it is fixable. In tough games (you can do anything old thing and win in easy games), McDavid and Draisatl are usually ineffective without both being on the ice at the same time: They've just played too long together, and have a symbiotic relationship to each other to where the two individual parts are less than the sum of the whole. This is why Woodcroft was having to put "McDrai" together almost immediately against Vegas.
The problem with that is that the tougher teams have realized that the Oilers' other lines become largely ineffectual, so when McDrai are on the ice a great deal of attention is placed on neutralizing them to the exclusion of everything else going on, with the idea that the game will be won at the level of the lower lines. The result of this is that McDrai end up having to play more than they probably should to keep the game from getting out of hand or to protect a lead, and by the end of the game are simply worn out. Thus, the frequently late collapses of the Oilers after an unreal early performance only because McDrai are totally gassed by the end.
So not only would a presumably new coach have to get McDavid and Draisatl to buy into the idea that they need to be 200' players to win championships, the new coach would also have to force them to split apart and stay apart except for PPs -- and to learn to be more effective when not constituted as McDrai.
That's all a big ask.
It also highlights the Oilers' real problem in that they may have two superstars but much of the rest of the team is arguably below-average, which no new GM or coach is going to fix anytime quickly. Woodcroft is a good coach, but he's having to play a losing hand when things go deeper into the playoffs and it is no longer a cupcake every other night.
IMHO, the obvious starting solution is to trade one of the two (Draisatl is probably the easiest to move) and build some downline depth, as well as sever the symbiotic relationship, but we all know that ain't happening. To the contrary, after next season when Draisatl goes UFA he will probably demand pay closer to McDavid and the Oilers will likely pay it, and then there will be even less to spread around the rest of the team.