I don't think they were because they saw glimpses of genuine class at the age of 16, 17 and 18 before he'd even went on loan, there was a load of talk about him before then because he'd shown a bit of special quality that let you know, if he developed as you'd expect, he'd become an excellent player and definite first-choice. I don't think we saw that with Cleverley before. Or if we did, there was so little talk of it that few paid attention. We've had people like Rossi or Welbeck come through with plenty of praise from the manager, we have people like Pogba and Morrison currently getting plenty of praise from the youth coach - Cleverley never had this level of exposure at a young age.
More than that a lot of fans hadn't got a chance to see him before this season (he'd made, what, 5 non-competitive appearances before the age of 22!) and, because of this, people are wary of talking about his potential first team merits before seeing more of him. Part of its probably to do with how early players are judged now, that patience with young players is lessening every year partly because of players like Messi, Rooney, Fabregas and co. being genuinely excellent players before they're even out of their teens, I think. Another part of it is that because people are so desperate for a superstar midfielder at this time, that pretty much every midfielder that's talked about by United fans is being compared to someone like Sneijder, Modric and co. never mind being compared to Scholes, and asked if they can do the job at the same level. If they can't, they're not good enough.
I'd said this time last year that I thought Cleverley might go on loan to someone like Sunderland, Newcastle or Bolton, have an excellent time of it, and then make the permanent move for decent money. I'm already well on my way to thinking I was very, very wrong - but I think he's surprised a lot of people. When Sir Alex was talking about him last year, he talked about his versatility his ability to score goals. Martinez talked about his intelligence being a level above most others his age (yet played him out wide). Or he was praised for his tireless running. There wasn't a lot of talk about how technically adept he was. Intelligence and energy are a very useful combination - as we see with Park - but they alone don't make a player good enough to start for us, especially not as a Scholes replacement; which like it or not people will be regularly (subconsciously or otherwise) comparing him to in terms of the levels he needs to be reaching, the qualities he needs to show. In the same way Carrick was and is still compared to Keane. And it's for this reason that Cleverley might not have impressed some people creatively, I suspect.
There is an unfashionable factor to it as you say - he wasn't talked about much, we never saw any glimmering potential from him in Carling Cup games (which was obviously more to do about him being on loan, but still), and he didn't really have any standout moments when he got his loan in the Premier League (in the way that Welbeck did, for example). He just kept plodding away, improving gradually, adding this and that to his game and performing his role with discipline and maturity. It'll take time for people to really get behind Cleverley and know what to expect from him. Have to say though, the early signs in his United career are promising.