If we were doing that we wouldn't be so heavy with the loans. We're going to have to replace 4 1st team players next season even if we're still in the Championship. That's before you have to replace any players that leave, or any players that aren't good enough. We've practically got a full rebuild to do already. The low and slow sustainable model doesn't rely on loans, it relies on development and you can't do that if you have loan players taking the spots. Roberts looks like a good keeper but aside from the odd injury we're going to be developing Man City's reserve keeper so they can get a bigger profit when they sell him on in the future instead. Fulham's striker might get 20 goals and a hefty price tag so we can't afford him. Giles is an assist machine, we'll never be able to afford him but Wolves will benefit from him improving his defensive side.
The idea of being sustainable is sound but we're not doing that. We've tried to spend big and missed out on targets, we've completely ignored our DM position, which we tried to recruit to last year (Siliki) so we know it is a weakness. If you are being sustainable then you sign players permanently, give them a chance and allow them to develop. We haven't got a squad, or made signings, that suggests long term sustainability. We've signed a CB to replace Fry who was developing well and we could've made a decent profit on. Not playing him means his value will go down. That's the opposite of what the process is supposed to be. We've signed short term loans etc. None of that is long-term thinking.
The major factor at the moment though is Wilder is not a manager who develops players. He doesn't trust young players. I have a friend who's son played for him at Sheff Utd and, similar to what we've heard from him about the youth not being ready yet, said there will be no youth development while Wilder is in charge. He prefers experienced players. He also said Payero wouldn't last long because he prefers players that have experience of the league they are playing in (and especially wants players that speak the language fluently). Obviously if a player is good enough and impresses they'll get a chance but the default when a player is injured isn't to promote the best youth player but to move an experienced player from another position to cover.