(Spoilers Main) One of biggest plotholes in ASOIAF's worldbulding (in my opinion)

The Valyrian Freehold. We know little about it, but it prospered for something close to 5000 years before the Doom, while having 40 dragon riding famillies ruiling it, or fighting for power inside the Freehold (since it was never a monarchy). This is insane. Am i the only one to find this ridicoulus ? I mean this is ASOIAF after all.

I know the Valyrian Freehold was inspired by the Roman Empire (the Senate for its from of governement, and the Empire for its size). But they became an Empire soon enough and roman politicans fought "only" for that position of power. In the Valyrian Freehold, you have 40 dragon riding familles all scrambling for power.

It's easy to understand how they would conquer and crush the rebellions of the people they conquered. In fact, with hundreds to thousands of dragons, they even should have conquered more. But how did they avoid in-fighting dragon warfare ?

Yes, the Valyrians would have an insentive to stay united in order to keep their numberous subjets in line. But what about the Game of Thrones ? You mean to tell me that during 5 millennia, their were never a single all-out civil war, a single rotten apple that wanted to take the power for himself, or any violent political uprisings or plot between the 40 dragon-riding famillies ?

It only took 130 years for the Dance to take place in Westeros. So imagine what a civil war like that within the dragon familly would have been like, with hundreds of dragons on each side. Valyria would have destroyed itself. Can't believe any of that never happened.

Feel free to tell me if you agree with me here, or if i'm totally reaching tho.