I don't think anyone looks back at those three windows and thinks it was a good time (although there is debate as to why things panned out the way they did) but we can't keep rehashing the past. It happened, we can't change that, but we have spent since, and even then it hasn't all been successful either.
I think it's still a bit too soon to say "still we won’t sign any new players" - there is still time and we know of at least a 3 or 4 negotiations that are seemingly underway for inbounds, plus the attempts to find buyers or loans for Ndombele, Dele and possibly Lo Celso.
We need to get enough business done this month to see us through to the end of season, hopefully finish in that 4th spot or at least be in the mix until the very end, which in turn will make us more attractive to more players in the summer window.
You are right that we have a top manager and we definitely need to support him. But Conte himself has said it is going to take time to fix everything.