Several of those players get in the current City side. All of them were world class. That squad is better than this one, that's unarguable. Football has evolved but those players were all much better when compared to those from other countries than this current squad. They weren't rotten personalities either. They were committed to club football and the England managers were unable to create an environment of unity and commitment to the national team, in combination with being tactical incapable of getting the best out of them.
What Southgate has achieved with this squad over the past few tournaments is very good. I feel like he's benefitted from some favourable draws and he definitely isn't as tactically astute as many other managers, but whilst someone else could improve on that side, it's no guarantee they'd be able to create the same team environment and that plays a huge part in things.