If someone with very deep pockets, and a good team in place, bought the club tomorrow, I reckon it would be at least 2025 before they could even begin to think of being seen as a major force in game again. Their problems run that deep and they’ve fallen so far behind. Ceteris paribus, players looking to play in the PL must prefer at least five English clubs over united at the moment. That’s probably the first time that’s been the case since WW2; and there will be no quick fix, either.
The stadium’s started to like very down-at-heel and in need of a few quid spending on it too.