What is your opinion about Heroes IV?

It's just that not everyone wants to learn something new. It's easier to say that something new is a terrible project, and you'll immediately find hundreds of like-minded conservatives. So, the third game is considered a classic of the genre, the fourth is an innovation, and the fifth, for example, is essentially a mix of the third and fourth. Well, the developers couldn't, despite the blind hatred of the masses towards the fourth game, make the fifth game solely based on the third, because there are too many good ideas and ideas with continuation in the fourth.
After all, it's hard to imagine the fifth game without its skill trees, without unique schools of magic, and not the third game's elemental ones.

and to conclude...
The fourth game is a wonderful, UNIQUE part.