Gray is fine in a system that affords him space, absolutely. But you still need end product on a consistent basis - he will never have that. He just won't, he's 26 now.
That's not to say he's a huge problem but when he's your best out and out attacking player then ultimately you can't expect to be anything but a team battling relegation.
That's not to say it's acceptable to be where Everton are, but ultimately if you rely on: Iwobi, McNeil, Gray, Gordon, a half-fit Dominic Calvert-Lewin, and then at the other end Patterson, Mykolenko and CBs each with glaring weaknesses (Coady and Tark defending in space, Mina being made of cheese, Myko being rubbish) then it results in just a bang average squad.
Everton need a manager that can overachieve by dragging this current squad out of the mire and even then I don't think that will be enough. I'm not talking about avoiding relegation here, I'm talking about avoiding a scrap. This squad isn't good enough to not be in a scrap, it's not a mid-table squad. So if nothing changes with the squad then I don't care what manager we have in, we'll be in a fight come the last weeks of the season, IMO.
Add in 2-3 options (for me a striker, a creative player and I'd argue a right-back) then it's a mid-table squad and then a manager (one better than Lampard, ideally) would be expected to get us there. Without those players then no, sorry, we're where we deserve to be.