You can choose to not accept it if you want, but it isn't going to change anything. This is what we got this year.
And Key is just one guy. If you think one guy makes the whole team you are mistaken. None of the top teams are where they are because a single individual.
James Allison was praised as one of the best engineers in the grid due to the utter dominance Mercedes had in the previous era. What happened to him now? Did he lose his edge?
No, he did not. It's just that his impact on the final result is severely overestimated by everyone. His contribution to the lack of pace Mercedes has now, is pretty much the same as his contribution he had on Mercedes' advantage previously.
It's just that as a team, Mercedes got it wrong this year, just like McLaren.
But the difference McLaren has to Mercedes is that their lack of (relative) pace to the front is somewhat justified by their inherent infrastructure deficiencies. And honestly, it's not even that big of a deal as people are making it out to be, that's why I say relative lack of pace. Because McLaren is still 4th, just like they were last year, just a little bit further behind in terms of gap to the top car. And if you expected them to suddenly fight for championships because of a rule change, while being at a significant resource and infrastructure disadvantage, then your disappointment is caused by your misplaced optimism for this season.
I myself was disappointed after Bahrain, because I thought they had gone back to being backmarkers, but as the season progressed, I honestly don't see this season as being that bad for McLaren. I expected them to be 4th again this year, although I admit, I hoped for them to be closer to the front.
Nevertheless, there are positives to take because it seems like they have finally broken the old performance barrier. The car is no longer bogging down on slow speed sections. It's annoying that the car is draggy as f*ck at the moment, and that they are lacking peak downforce compared to the top teams. But these two things have usually been the easier things to strengthen in your car. The difference was almost always made in the very technical slow speed corners, and they have actually improved massively in that area (comparatively with previous years).
With the investments and the budget cap slowly kicking in, I can see positive things for McLaren in 1 or 2 years.
So long story short, if you keep your expectations at a realistic level, you will enjoy the season more. I understand that with the long wait we have had, patience is running low at the moment. But right now, more than in quite a while (well perhaps with the exception of last year), there are positive signs pointing towards the return of a competitive McLaren in the nearby future.