England's bad defense gets overstated, IMO.
Stones is a genuinely top CB. He is very very good. It would be nice if they had someone better to pair with him (hopefully that will eventually be Colwill, although I say as a Chelsea fan that it's not Colwill yet), but - I sound like a broken record on this board - Maguire has been consistently stellar for England in ways far far beyond what he is at club level.
It would be nice if Reece James could be fit and healthy, but Kyle Walker is a better right back than most countries can put in that spot. Not even getting to Trent, who I do think likely plays in midfield for England.
Shaw/Chilwell at LB is a weak spot, simply because neither of them is fit enough to get into a good playing rhythm. Left back is IMO the one position in the England squad where you can comfortably say they are worse off now than they were in 2021.
Funny enough, part of what makes Southgate a miserable manager to watch and not the manager to take this team forward is that he overcorrects based on the notion that his defense isn't particularly good. It actually is a sufficiently decent back four that he doesn't need to play as negatively as he does, especially given that his main full-back options (given that James and Chilwell are generally on the sidelines) offer more defensively than they do going forward.
The problem ain't personnel, and it's seldom the team selection. It's the tactics with the guys on the pitch.
You're probably right that results have had more to do with the coaching than the personnel. And I fully agree that Southgate's fear of their defensive shortcomings has neutered them way more than he should've...like I said, if they just had someone like Flick, I'd rate them very differently despite still being very meh on their defense.
I'm also probably over-critical of anyone's defense unless they have France's depth because of my frustration over our current down period...and I admittedly don't watch the EPL enough to have strong feelings about English-Süle, Colwill, or whoever else Southgate has to pair with Stones.
Plus I don't rate the English keepers much at all based on what I've seen of them for their NT. Could totally be a ter Stegen thing were they're just not as good as for the NT as they are their clubs, so I could be under-rating them.
But from where I sit, looks like they have mediocre keepers, FBs who are either constantly injured or defensively mediocre, and mediocre CBs around Stones...and I'm not sure if Stones is good enough to anchor an elite unit or if he needs to be the 2nd fiddle like a better Rüdiger.
And Southgate just exacerbates those issues with his refusal to accept that their strength is further up the pitch.