Open play wise, we have been getting better at defending. The issue clearly is defending set piece, especially aerially, which individual ability is as important as tactic. We lack good especially dominant header. We can't do man to man marking well since opposition would outnumber us with their aerial threat targets during set piece.
It's misleading that everyone is criticizing Dier for Everton goal. Dier was supposed to cover a zone that contains Calvert Lewis and Michael Keane, 2 serious threat. 2 vs 1 against through out. Not like what we saw at the end that Calvert Lewis taking on our 2 CBs. Calvert-Lewis should be Toby's man. Dier reacted well to pick up Calvert-Lewis but he was already at disadvantage. That's one heck of a whip, always favoring attacker over defender. May question Dier not attempt to jump, but jumping then would make no difference. Running toward our goal and jumping is difficult to get elevated especially when the ball is behind you.
Calvert Lewis made a straight run, nothing special or man marking mistake from our player. It's the lack of individual ability that forces our set piece defensive line spread so thin having to to worry about near post and far post area. As it played out, even Richarlison got free, with Toby completely got occupying by him to free up Calvert Lewis. Similar thing happened with Davies got pulled out of the equation by Mina who wrestled Sissoko.
Poch team building is clearly flawed, which even at our bets under him, we always had this Achilles' heel in our game. It gets to the point that even when we rival other team on the attack, and play well overall. One a few moment cost us not just the whole game, but even the season. The solution should be paying to get a more capable header into the team, and CV & Rodon may be the first step helping the situation.