When did plot hole = things I don't like about a movie.
In this case, it's not. DOFP's whole "Mutants losing in the future" thing is a big plot hole considering the kind of powers we see them using. Unless they're total incompetents it's implausible that they'd be losing so badly and let the Sentinels get that strong. Quicksilver still would've been around when the war started and with his powers there's no way they'd have lost.