Heroes VII

For example, I didn't find the battles or units in the game to be very interesting.

Well, let's put it this way. From a tactical point of view, they implemented many things that you yourself considered important (relatively low movement speeds, for example). Other things (like the ability for some ranged units to move before/after shooting, flanking/rear attacks, obstacles that hinder shooting) can't even be implemented in the fifth installment, but they are quite interesting.
Another question is that many abilities have been introduced into the game somewhat randomly, and in fact, due to their poor implementation, they don't add much variety to the tactics. Weak synergies, and so on...

the game isn't very well suited for Multiplayer (too slow development)

Actually, I saw a review somewhere that explained clearly that you simply don't need to develop extensively. The main thing is to build a base and upgrade a basic unit (an enhanced basic unit, which is usually not too far down the development tree), maybe add a few elite units, and you can already finish the game if you maintain the appropriate pace. Although, with this approach, some of the content is lost, of course.