I'm not really that sold on Morata and i'm open to be informed by those who think otherwise. I have seen him play since he was newly promoted at Real Madrid. Even his best career years (@Juve) have poor goal records. He has good movement and decent strength but his assist numbers were not good either. People keep bragging about his years at Juve but even at that age, Carlos Tevez was a bigger hit. They won the league every year since he left and arguably got better in the CL. It seems like playing even Mandzukic at this age is not making Juve fans miss Morata that much. I think Belotti, Lukaku could've been deadly for them. They were missing goals, needed a finisher not him. Also, i don't think he is Mourinho's ideal type of forward who has physical presence like Drogba, Costa, Ibrahimovic.
I agree with you on Morata, that indeed, he just doesn't seem a world class talent. He is a decent player alright, but he is just not there.
With the rest, I disagree though. That Mandzukic plays for Juve and they don't miss Morata, how much of it is actually one player being more suited to Juve tactics? How much of it is because Juve knew that Madrid would take Morata back if he kept playing and doing well? Italian clubs do this all the time with players who they might lose. Juve of course were happy to keep Morata, they offered 30-40m to Madrid in addition to whatever they paid initially for Morata. You don't do that for a bench player who you think is worse than a 31-year old workhorse in Mandzukic. You gotta learn to read between the lines. Mandziukic is a player who will barely command a 15-20m fee these days, and he was playing ahead of Morata for other factors than quality, IMO. Let's remind ourselves that Mandzukic couldn't cut it at Atletico even when he essentially had no competition for his (striker's) position. I thought he'd be perfect for Atletico, but he really disappointed. Simeone, on the other hand, would love to get Morata these days.
I also disagree that Lukaku and Belotti are so much better than Morata. These are all about the same caliber, give or take. Lukaku, you may argue, is settled in Premier League, but he is massively overrated. Watched him for Everton loads of times, and he just isn't worth 100m (neither is Morata worth 73m). If ManU wanted proven quality, Griezman was their option.
In conclusion, even if ManU bought all of Belotti, Lukaku, Morata, Perisic etc., I just don't see a single world class talent in there. They would improve, of course, just cannot see them becoming a top team.