I can relate.
My son is 8 now but he has always been hard work.
He does have a lot of great qualities but he can be stroppy, defiant and just downright awkward and often nothing can please him. He is very bloody minded and can be horribly obsessive about things in a way that upsets and disrupts everyone around him (this is one of the reasons we did often consider some sort of neurodiversity, but the older we get the more we don’t think it is).
I think a lot of the issue with my son is that he is very spoilt. We just love him and want to make him happy but we have realised this is not always for the best.
He does, however, know when his behaviour is not acceptable. And we know this because he would not dare try it with other people. Just with us.
On the flip side, he is actually very mature for 8, has very good manners (particularly with other people), is very funny and engaging, outgoing and confident.
Sometimes I will be feeling frustrated at how difficult he can be, then I spend time with his friends….and I find them irritating beyond belief.
So a lot of it can just be that young boys can be very annoying.
edited to add: my son is not an only child. So we do know how other kids behave. And when I say he is spoiled, I don’t mean obscenely so. We do try and instil in him that he is not the only member of this family…but he sometimes does act like he is. He does have a way of very much ruling the house, which we need to stop.