Walker was a wide man when he was at Spurs. Not sure why City, and England, are playing him as part of the back 3. Maguire has had a good tournament, other than the dive in the Colombia game, and he'll be an asset going forward. Stones is also a decent defender although I don't think he's up there as a world class player yet.
Bigger issue is at left back. A fit Danny Rose would have been an asset. Without him they're relying on the likes of Ashley Young. That's not a good situation to be in. Sessignon will be old enough to be a viable England contender in 4 years time - perhaps he's the solution but he'll need to be playing for a better team than Fulham.
As for midfield - they've had a few players over the past few years who have promised but who then fail to deliver. Ross Barkley was one but his career hasn't panned out as hoped. I don't see Lingard as the answer and Sterling is either good or garbage. Rashford might develop into a good option who can link midfield and attack, play middle or wide and come in from deep to support Kane? If Rashford is the option on the left and Alli the option on the right then they really need those 2 to mature and gain a bit more game intelligence or to find a midfielder who'll bark orders at them and show them where to go to pick up on dangerous passes.
The tournament has been interesting to watch from a tactical viewpoint. The back 4 seems to be less favoured these days. If managers are abandoning 4-2-3-1 in favour of what's effectively a 3-4-2-1 with the 2 wide midfielders expected to be wingbacks and the 2 players playing off the main striker expected to cover across the whole width of the pitch then it'll create some interesting opportunities for players and demands on coaches in the next few years.
I've disliked the possession-heavy, short passing football of the past few years. Klopp's Liverpool with their high pressing game is something that I enjoy watching. Kane is big, strong and talented enough to lead the line but perhaps he's not yet ready to do so and lead the team? That could work well for England but only with the right additions to the squad.