No one is really criticizing the fifth game; it's just not fully thought out. And apart from the more advanced graphics (considering the year), it didn't stand out with anything revolutionary. There's no market or upgrade system like in the second game, etc. The hero tree is just an unnecessary thing. It's the same principle as in the third game - super-heroes, good, so-so, I don't want to see.
It's hard to believe in an interesting sixth game, although if I'm wrong, that will be better.