While that may be one criticism, I don't think it's the biggest criticism. I think the problem with Civ5 is that they've changed things in a way that makes the game worse rather than better.
To give a couple of examples:
1. The one-unit-per-tile rule. That was something that I think many civ4 people - including myself had been asking for for a long time, so superficially it was to be welcomed. But then when Civ5 actually arrived it turned out that Firaxis had apparently not thought through
how to implement the change. I'm sure for example that almost noone who asked for that change intended that you'd be prevented from improving a tile because a civ you've got open borders with has a unit there. Or that Firaxis wouldn't make the effort to program an AI intelligent enough to fight with the new rules. If Firaxis had considered these types of issues I imagine Civ5 wouldn't have been so unpopular.
2. The new way of changing 'civics' with culture seems nonsensical. In Civ4 it worked quite well, and - importantly - it was slightly realistic. It made some sense that you couldn't swap to a new civic until you'd discovered the knowledge for it. In Civ5 they've changed from a system that worked to a new system that is no better, and is actually less realistic to boot: How can the amount of culture you've acquired so fundamentally determine which civics you can use? It makes almost no sense. So why make the change?
3.
City states. Great innovative idea. But ruined by the fact that it's so formulaic. For example, you give the state a prescribed amount of gold, you get certain benefits for a fixed number of turns. The whole dealing with city states thing is not much more than manipulating a simple (and boring) mathematical formula. Admitted parts of Civ4 are a little formulaic but -on the whole - nowhere near that bad.
Those are the kinds of things that put me off, and I get the impression from the forums I'm not in a minority
If I was to summarize, I'd say that the problem with Civ5 isn't so much that they've changed Civ4, it's that they've changed things that there was no need to change And even where there was a need to change something, they didn't think it through. Civ4, when it was released, gave the impression that Civ had been changed to make it better. To me, Civ5 gives the impression that they've changed Civ for no other reason than for the sake of changing things.
Contrast with Civ4 where they changed loads of things from Civ3, but in almost every case, you could see a good reason why the new system was better: More realistic, more exciting or subtle gameplay, etc.