Even a not-so-successful installment is discussed thousands of times more than the seventh one. Does this mean that "Heroes 7" turned out to be even worse than "Heroes 4"?

And that was a risky statement! Fans of the fourth game, on the contrary, consider it a breakthrough. Many others simply see it as an misunderstood, but good game. I personally love the third, fourth, and fifth games... Therefore, I wouldn't say so bluntly that the fourth game is bad. I only saw the seventh game in passing, but knowing that it was developed by Ubisoft, for whom the Heroes series has long ceased to be a priority, and that they didn't put much effort into its development, I can assume that, objectively, the seventh game was a much bigger failure for its time than the fourth game was for its time. And if the fourth game can rightfully be called simply an misunderstood game, then I'm afraid there will be no excuses for the seventh game.