Hell, does anyone perfectly explain everything to each other all the time in the real world?

No, so this argument fails there too.

In the story we just don’t know why things aren’t disuccessed “perfectly”. Like why does Hermione not explain to Ron that she likes him, instead she has a fight with him. Wasn’t that an issue for OP? (It wasn’t for me, because I understand emotions challenge us to communicate well, and I’m an old fart without the hormones of a teen).

Kids world and adult world are separate. Kids very often don’t want adult involvement in their world - they see it as an intrusion. There’s also a general distrust of adults: “you just don’t understand”, or “things are different now than when you were my age” are the refrains we hear every generation. Again, I’m old enough to have seen this several times.

And the adults are busy with their own responsibilities, so won’t always catch on to what’s happening in the kid’s world.

Most importantly, the adults have to allow kids room to figure things out on their own, to struggle with difficulties. Always being there means the kids never learn to solve problems themselves, to build their own relationships, to figure out how to identify good people, etc.

Also, people are human, warts and all, communication is hard.

As a kid, getting explanations for things out of adults felt nearly impossible. I’m sure part of that was my phrasing as a kid, I just didn’t know how to formulate a good question, plus adults surely thought I was often a smart ass or just asking dumb questions with obvious answers.