The 2nd-best England manager ever in terms of results (and even Alf Ramsey failed to qualify in 1974, so...) and a fundamentally decent and scandal-free man which - given Hoddle, Allardyce, Eriksson, Capello - is strangely quite the achievement. He is not a world-class tactician but his understanding of that specific role was second-to-none.
I think his detractors will regret what they wished for if we get the opposite: a world-class tactician with no understanding of the role. That's what Capello was, and nobody has botched an international tournament worse than Capello in 2010 given what he had available. If Southgate's replacement tries to make the beast that is the job submit to their own managerial foibles, rather than understanding the job's unique demands and molding themselves to it, they will fail way worse than Southgate ever did.
Not to be confused with XIII_Minerals.