I'm no Southgate fanboi, and I get just as irate as any sane fan with the team selections and the favouritism at times - but you have to look at these things in the cold light of day. You mention the talent in the squad - that 2018 team was crap! The midfield in particular was horrific. Much more talented England sides have departed major tournaments way earlier than that shower of shite.
By the time of the Euros, the squad was in better shape, but still no functional midfield - that's what got found out against Italy - and that was a very experienced Italy side playing well containing some great players for whom it was a last hurrah. At any point over the last 50 years that Italy team would have been kryponite for England. We still (and the young players are way ahead of their peers from 10, 20, 30 years ago) are not quite technically as good as the very best on average.
In the last world cup we came up against the best team in the tournament (player for player) a team of grizzled winners, containing the best player in the world who had already set the tournament alight and would score a hat trick in the final! And it was a good game which we were a tad unlucky to lose in normal time.
With a better manager, could the details have been tightened up and might we have won those key games? Maybe. Has our performance been massively under par? Nope - unless you think we have the best players in the world. I think they're very good, but not as good as France's for instance. And our midfielders are nowhere near as good as that Italian team's.