Okay, since you clearly don't understand basics. Kanchelskis came to United at 22 and by the time he was 30-31 he was pretty much done and could not continue to play in PL. Shevchenko went to Chelsea when he was 30, after spending like 7-8 years in Milan, so it's no wonder he could not handle the PL intensity.
Some players can play into their 30, but you have to be very fit for that. Neither Shevchenko, nor Kanchelskis weren't the fittest players, they were miles better than the likes Arshavin that failed miserably, but they still come short when compared to say Drogba or Lampard.
Yeah, based on youtube cuts, never actually seeing the guy play and decent number of games. As i've said you are missing that he is very inconsistent and sometimes drifts off in game, it could be easily seen in Kiev's match with England, he posed no threat whatsoever then.
That's actually you who are being ignorant and very immature at that. You know nothing about football in Ukraine, you don't realize the magnitude of the task at hand. You don't know that ukranian clubs are playing until late november or early december at most, then hey go for a 3 month off-season rest/training to to play again only in march. And they also have a month of mid-season in summer, usually in July. So the regime that Konoplyanka is used to is very different, it is completely different to any other top league. And move to Spain, Germany, Italy would be a real test of his general fitness, stamina, ability to get used to much more tougher and demanding regime. And that's Spain, Italy. As we know England is hardest of them all in that respect, without winter break at all, with much more pace in the games, where much more work rate and running needed.
So it's all raise a legitimate concerns, whether he can actually make it here. Especially in the top club like Manchester United. And you are being extremely ignorant by simply brushing them of as insignificant.