It's not so much the not winning anything; Moyes has never really come close to winning any major titles, in spite of having managed sides that were amongst the wealthiest in the league. Neither he nor Howe produce outstanding sides who play brilliant football against the very best. In short, they just don't know who to win at top level. Any manager of an England side needs to be able to do that, and the pool of candidates is vanishingly small. Southgate has surprisingly been the best for a very, very long time. And I never said that any England manager has to be English. I don't subscribe to such nonsense.
The question to ask is; would Moyes or Howe get the top job at say Liverpool, Man City, Barcelona, Bayern Munich, Real Madrid, AC Milan etc? Of course not. And I think there's the answer as to why they shouldn't be England manager. Not that Southgate would either but he has at least been moderately successful so far.
Beyond that; I also think one major issue is that the top English teams are all managed by foreigners. Aside from Bacon Face, who are/were the top successful managers on the EPL? Mourinho, Benitez, Ranieri, Wenger, Perp and Klopp. All have introduced superior playing styles. So any English manager, used to the level of mid-table clubs, doesn't know how best to play the various players properly, cos they don't know that better style of management. Roy Hodgson, Big Sam, Turnip Head and the Wally with the Brolly! 🤣 I mean, come on. Southgate is light years ahead of any of them!