They have better midfielders. Strinic, Lovren, Vida and Vrsalijko are not better than the defenders Southgate had available. Strinic is a below average fullback playing for a poor A.C Milan team, he's a limited at best player. Rose and Young (Or Delph, who was very good in that position all season for City) aren't great, but are better players than him. Heck, so is Ryan Bertrand ffs.
Lovren is routinely mocked for being incredibly error prone. He can look decent all game but is generally always good for an error, I don't know a single Liverpool fan who doesn't get scared watching him play for them. Even when he's looking great you can't trust him. He's no better than John Stones. Vida plays in Turkey and is (again) very clearly a limited defender, how many teams would take him over Maguire? Seriously? Both him and Lovren looked terrified when England actually got at them for the first 20-30. Vrsaljko is a good player, but he's no better than Trippier or Kyle Walker, looks like Dani Alves in his prime when you give him the freedom of the right wing, of course.
They're better coached, but that's surely down to Southgate. He's the manager, if we're not a well coached side then he has to accept criticism. I like him, he's obviously well liked and has the team united which other England managers have hopelessly failed to do, but he failed tactically this tournament. His successes elsewhere mean he deserves another chance, but there's no point denying the truth. We don't need to pretend Croatia are fantastic now, they aren't. They're undeniably a good side, with good players, but they too struggled their way through the knockouts. Personnel wise they're on a similar level to England, though I think on paper we have the edge in terms of attacking and defensive players, while they obviously have better midfielders.
We should have beaten Croatia. We took the lead and they were all at sea for the first half, could easily have been 2 or 3 nil. When they got on top and we were clearly on the ropes in the second half, he was reactive rather than proactive, and never did anything to remedy the acres of space they had down the right which led to the equaliser. Managers are paid to steady the ship in these situations and work out what is going wrong, it wasn't a case of playing against unstoppable, vastly superior players who he could do little to stop. He was poor, but he deserves time and respect for rebuilding a sense of belief in the England team, and he will get that.