Nature Structures

I don't want to say that Charm is bad. Not at all. But in my opinion, it's inferior to Summoning. Summoning is definitely not useless. It summons "its own" units. Perhaps not many at first. But it just needs to be leveled up like any other skill, improved. I won't even mention the artifacts that enhance it... because I don't really respect relying on luck. After all, artifacts are a matter of chance; sometimes you have them, sometimes you don't.

First, it's not necessary to take "enchanted" units into the army; even before Equilibris, they appeared nearby if they weren't taken into the army itself.

I honestly didn't understand this phrase.

Secondly, the example with titans and dragons is an extreme case; Charm is much more effective at the beginning, when you already have your own unit standing on one, or even two, mines. And if you have halflings... then it's a real fairy tale.

Is this when you have your own units standing on the mines? I always have something other than dwarves or halflings. I admit that this might happen, but it's very rare. So, yes, it's a fairy tale.

Regarding Summoning: first, it's useless at the beginning; summoners simply clutter up the slots and reduce the already small number of summoned units (if there are many slots, they will summon all units of that level in turn). As a result, in one week, you can summon about 7 fairies and wolves, maybe a little more, but usually less, while with Charm, you can gather so many squads in one day...

From these words, it's immediately clear that you don't respect Summoning. And, most importantly, you haven't really tried to master it. What does it mean to clutter up the slots? Just make Summoning work for you. Don't just stand there with your arms crossed, foaming at the mouth, proving that it's useless. Leave one slot free, and that's it! (that's what happens when you take Summoning level 1; one or two slots remain free). And then choose who you want to summon. If you don't like a leprechaun, dismiss him or send him to the mine. The next day, he'll summon you a fairy or a wolf. Seven fairies will be too many for you. Have you ever played on Champion difficulty? When every penny and every unit counts. And here, you're getting it for free, and you're still complaining...
Oh, I have to teach you everything!

Summoning won't be useful either at the beginning or at the end of development; it's only useful in the intermediate stage; you can use it to replenish squads of tigers or elves.

Exactly. You keep repeating the same thing. But what about wolf and fairy squads? Don't they need to be replenished? Or are elementals not useful to you?

In general, the advice is to get the maximum benefit from the skills.