When did we ever sign the likes of Mbappe?
An Mbappé type of signing probably hasn't happened, but what I meant was that he wouldn't consider us either right now.
You could argue however, that Pogba had a similar reputation to Bellingham's, when he joined us as a 23-year-old old in 2016.
Also, Bellingham would've been an incredible signing, even for 100+ million and even though he's one of the most coveted youngsters of the last few years. However, he would've had to understand that at best, we are still ~2 years away from challenging for the title, and we'd have to get every signing and decision right for even that to happen.
It's also important that we sign players who are ready to make an immediate impact, even if we are not one of the best sides in Europe just yet. Sancho was someone who could be a useful player for City or Arsenal right now (with the right attitude, obviously), but he was never going to carry this United side, because he's not someone who can thrive in nonoptimal circumstances, and that's not even down to his apparent lack of dedication, but rather to his profile as a player. He's a great link-up player, who can play a part in a good team, but isn't an outlet like Rashford or even Garnacho, that's why he's never been able to shine at United.