He is better than all of those players. The only ones who disagree at spoilt United fans who are never happy with what they've got.
If Modric, Kroos, Vidal or Thiago were here, they wouldn't be doing any better than Pogba is. Physically, he is much better than any of them.
As for your first bolded sentence, there is no evidence to support your claim that Pogba is/will be better than Gerrrard or Lampard. If he did for 5 consecutive seasons, I'd take that right now., even though that still falls short of his fee and hype.
Re the 2nd bolded sentence, having been a United fan for many decades, Ive been more than happy, like more than more happy with many players we've had down the years. Likewise I started supporting United when we won nothing. So I do not meet either of your surreptitious criteria.
Number of things that require urgent improvement:
1. I dont know what he does. So far, he has failed to be an effective no 6, no 8 or no 10.
2. I've read claims that he cant fulfil his potential unless he is surrounded by world class experience. I'd argue he looked good at Juve because of the work of his colleagues, not because he was that good. Juve carried him, as they are proving this season, they are perfectly fine without him.
3. He needs to score 12-15 goals a season. His failure to contribute is a critical reason why we have failed in top 4 stability, let alone mount a decent title challenge.
4. He slows our game down. He needs too many touches to gain control of the ball, be forward facing and spot an offence pass. He sometimes looks good because of his Hollywood passes, but in reality, only 1 in 4 of these are successful.
5. Which means he gives the ball away far too often.
6. Most importantly, he needs to dominate games, certainly against minnows and also regularly against top teams. He is supposed to be a match winner, if not through goals, then certainly through influence and assists. He is already 24: benchmark that vs Ronaldo, already a Balon D'or, Rooney, Giggs, Beckham, or even Keane, Gerrard, Lampard, Vierra etc at that age. They had found their voice and consistently bossed it.
I fear he may never crack all the above, and if he does, it will take years ... but then we shouldn't spend that kind of money on a player who is 5 years off his peak.