It might be true, though, that we haven't spend big money on a midfielder (not counting Arthur obviously, since his cost was 12m+Pjanic), because we couldn't find a worthy one to spend the money on.
We did spend 75m on De Ligt, about 50-60m on Chiesa, 40m on Cancelo, 35m on Bonucci, 35 on Kulusevski since we signed Ronaldo. We had the money, but we paid them for players we considered worthy. My guess is that we couldn't find a worthy and available midfielder.
My criticism towards Paratici and co. isn't about not being able to buy a 60-70m euro midfielder (because I believe they were willing to buy Pogba or de Jong, but teams wouldn't sell or other big teams would outbid us), but not being able to find a worthy cheaper, or a potential world class cheap(er) midfielder, like Marotta did with Pirlo, Vidal and Pogba.
Perhaps, and possibly, it wasn't easy to find such guys, maybe it was even close to impossible, but no one cares. It's their job to find these players, and they didn't.