- What are the drawbacks of Heroes 3? (What didn't you like about it?)

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By the way, you didn't mention that in Heroes 3, not only are many secondary skills not very useful, but there's also a problem with the primary skills. For example, attack is much more beneficial than defense, and magic power is better than knowledge (due to things like intelligence and mana vortex, which double the amount of mana).

In principle, there are a few (not many) skills that are not very useful, but everything depends on comparison. And if there simply weren't any great skills, then mysticism would be very popular. You choose the more useful skills, but you have to take what you get. It's like in cards - you expect to get 4 aces when you deal, but you get 4 sixes. And you'd probably like the deck to consist only of aces - but then the opponent would also get only aces...
"attack is much more beneficial than defense," especially for a tank (a unit that absorbs damage), who is constantly being attacked:D. This can only be useful for a gray behemoth, who doesn't care about the enemy's defense.
Magic power is very useful if you want, for example, to take down a diamond golem with its 95% resistance with a single lightning bolt. Especially if a mana vortex is placed near each enemy squad. And what if there isn't a single well on the way, and the warriors don't have much intelligence? By the way, as far as I remember, the problem with playing as a mage is the shortage of mana, which needs to be replenished frequently, and not the power of the spells. After all, cloning 1 angel and 10,000 angels costs the same. And you can destroy it in 1 round, even though you would have enough power for 50.
It all depends on how you look at a particular problem. And on the ability to get out of a difficult situation, rather than trying to adapt the situation to your needs.