Mourinho is right.
As a squad we do not have the mentality to be successful. People can point to last season's CL but we all know that papered over the cracks and was as freakish as Leicester's PL win (and ultimately we lost anyway).
To be a truly successful team you need world class talent and an obsession with winning, an arrogance even.
Who is world class in our team right now - Kane maybe on his day? And to be honest he's not the type of striker that can grab a game by the scruff of his neck and make some magic happen like Aguero but he is deadly with decent service behind him.
Aside from that, you look at the squad and it's a mix of a few good but not world class players (Son, ?) a couple of promising young talents (Lo Celso, Bergjwin), mid-table standard players (Winks, Davies, Dier) players with questionable attitudes (Aurier, Ndombele) and those who at times barely belong on a football pitch (Sissoko, Sanchez, Lucas).
I feel like the turning point was the Walker sale. We had a really great first XI at that point, with a mix of senior players in their prime and young talents and we should have pushed on. But instead we sold the best right back in the league to Man City so that all his ex-teammates could watch him go and get paid double their wages and win trophies.
We never replaced peak Rose and Walker and have been a shadow of ourselves since. Add to that the loss/decline of Dembele, Wanyama, Dier, Toby, Jan and Hugo and what are you left with?
The squad started to lose belief with each passing season as the gap started to widen between us and City/Liverpool.
So ultimately we are now left with a squad that lacks belief but more importantly lacks the quality to challenge for honours.
We probably are the 8th best team in England now and it will take some miraculous transfer dealings to get us back amongst the big boys any time soon.