Most definitely the case - hence the talk of appointing a Director of Football leaking out immediately after deciding not to pay ridiculous fees for the players Mourinho wanted.
To be honest, I think Mourinho has to shoulder some of the blame for the targets he picked.
For example, Maguire was technically available, but the talk of Leicester demanding a record fee (ie. in excess of the £75m Liverpool paid for Van Dijk) made it completely out of the question. Being the best player that we could actually sign in a specific window does not make him worthy of that kind of fee. Does anyone really think spending £80m on Harry Maguire would have sorted out our main issue -- attack? Of course not.
Whether or not Alderweireld was actually available is still a mystery. Maybe Levy would've sold him if he'd found a replacement first, maybe not. Maybe he demanded an attacking player that we would've had to replace first, maybe not. Asking to sign anyone from Spurs for United is a crap shoot, even if they've put in a transfer request.
Mina was a joke of a suggestion, a player that had only been in Europe for 6 months and had barely played before having an average World Cup made to look better by scoring on some set pieces. Throw in the alleged demand of a buy-back clause from Barcelona and there's no reason we should've been anywhere near him.
Boateng is permanently crocked, almost 30, and the most notable thing he did during his last spell in England was get himself injured by banging his knee against the drink cart on one of City's European away trips. Grasping at straws.
Skriniar and Koulibaly looked the business in Serie A and seem like Mourinho-type defenders, but there was barely a whisper about either.