I don't buy all this Jules, didn't Sanchez leave Barcelona because he wasn't the main man, ditto Ozil constantly getting subbed at Real.
...and when they are playing as in their current form there isn't a huge gap between their team mates, in fact there is no gap at all, they are worse.
I have no doubt any delays are all about money even if they come out and say differently.
This team finished 2nd last year not mid table... maybe the pair of them should be dragging the rest of their mates up to finish first, as D.Costa has been, ditto Messi for years, Ronaldo, Aguero etc... making the difference not hiding when it's crunch time.
I think there's a middle ground between being subbed quite often and being one of the two pillars that are expected to hold everything together.
It's too easy to expect them to carry the team week in, week out, just because they may have wanted to play a more important role when they left their last clubs. I cannot imagine Wenger promising them "You are going to be our two main men, the course of our season will lie in your hands." Isn't it more likely that they were promised a more competitive team in which they are key players, but not the only two world class players? We have never built this competitive team.
As for the players you mention that dragged their teams: apart from the fact that two of them are the best players of their generation, your examples prove my point. All of them had a better team to fall back on, and to push them. Do you really think Ramsey, Oxlade-Chamberlain, Walcott, ... - you name them - would play for Barcelona, Madrid, or even City and Chelsea?