What is your opinion about Heroes IV?

What did you expect from the 4th installment? A continuation of the 3rd? The 3rd is a magnificent game. Undoubtedly, the series owes its popularity to the 3rd.
But is it the best in the series? In my opinion, no.
After that, did you really need another 3rd game?

I express my agreement. I'd like to recall that we had a similar conversation about the 5th game, only you were on the other side... or not with you?

Regarding the statements. Have you actually played the 4th game? Not just played it, but played it thoughtfully?
An army without a hero is only needed to deliver reinforcements and simplify the clearing of the creeps that appear every month. It is unusable in battle because the Battle Doctrine practically doesn't work. There is no luck. It's just a large group of creeps. If you had played it, you would know.

I agree again. Only with one clarification: the army in the 4th game is generally not needed, only at the initial levels and in the Campaigns, when there is a limit on the hero's level, but in the 2nd-3rd missions of the Campaigns, it is also not needed.
It got to the point of absurdity. Not only did the army slow down movement, but when fighting neutrals, I had to separate units from the hero so that the valuable units wouldn't die. The hero is fine; he rests for a day, sleeps for a night, and is fresh again.
I'm not saying that the army is completely useless; sometimes it's needed as cannon fodder so that several strong attacks are directed at it while the hero does his job.
Therefore, I believe that the 4th game is more of an RPG than a strategy, and since I like RPGs more, I played the 4th game to my heart's content.

There are no unusable spells in the 4th game. If you have a different opinion, I sympathize. Name at least one unusable spell?

Again, I agree. There are no unusable ones – they all work. :)
Only when you have a lot of spells and there is something to choose from, you realize that most of them are not necessary, and you use the spells that are more effective. In this sense, there are many unnecessary spells in the 4th game. But, of course, this is just my opinion. :)