Onana is the only signing that you can argue was both necessary and will almost certainly prove to be an unequivocal success with time.
Højlund is a striker who - even if he was available to play - can't be expected to score at a rate that a top CF would, given that he's one for the future. You could nonetheless make the argument that even right now, injured, he is proving his worth by taking the place of EtH's buddy Wout, and thus depriving us of the sight of the lumbering oaf wandering on to the pitch (or worse starting). In a way, he was signed to save EtH from himself.
Mount is perplexing to say the least. Not as good as Bruno, not as creative as Eriksen and (painful as it may be for some) less immediately equipped to partner Cas as a true midfielder than Fred was.
This may prove to have been a brilliant window if Mount adapts quickly to his new role and thrives there and if Højlund comes into the team and drastically improves it.
But in many ways for this season, despite spending big on a CF, we are still reliant on Rashford carrying our goalscoring threat on his own (and we're fecked if he's injured or off form). Despite spending big on a midfielder we are still reliant on Casemiro holding together our midfield on his own (and we are just as fecked if he gets injured/suspended as we were last season).
In order to improve this season, we needed a Kane & Caicedo sort of window but we wound up with Højlund and Mount.
And if Rashford has a less than superhuman season, we're not going to make the CL, let alone dream of greater success.