I don't get these posts I've been seeing saying what has rhaenyra ever done to prepare for the throne/ prove she'd be a good ruler. Like did you watch the show?
In the first episode, before she is even named heir, she is cup bearer to the king, meaning she was present during small council meetings, observing and learning how the kingdom is run and governed. In ep 6 we then see that she has a seat on the small council and is actively taking part in the running and governance of the Kingdom.
She marries laenor, the son and heir of a powerful house, securing their alliance and providing her family with a powerful navy. Whilst also fixing her own father's political blunder in the process.
She has many children creating a line of succession (and no it doesn't matter that some of them are bastards as its just a rumour and can't be proven so long as laenor is claiming them as his.) We also see jace, her heir, learning high valyrian because he believes a good king should uphold the traditions of their house, we see rhaenyra guiding him in this, showing that not only has she been preparing herself to rule but she has also began preparing the next heir for his rule.
She spends many years ruling and governing dragon stone, which is traditionally given to the heirs of the iron throne as a practice run and specifically to help prepare them to rule.
I've seen comments saying that she should have done more to secure alliances with the other houses so they'd support her claim. But here's the thing with that one, how do you know she didn't? There were large time jumps between various episodes, we don't know what she was doing during those time jumps. For all we know she was inviting lords to dragon stone to maintain relations or visiting/sending other members of the family to visit other houses. I mean she seemed pretty confident and knowledgeable about who was and wasn't likely to support her claim during the council meeting in 1x10. Also those houses had already sworn oaths to her and those oaths don't have an expiry date.
I honesty don't know what more you wanted her to do. I think the show made it very clear that she spent literally pretty much her entire life preparing herself for the throne.
Meanwhile all we saw aegon doing is jerking off out windows, drinking excessively and harassing/r*ping serving girls. But sure rhaenyra is the one that should have done more to prepare/prove herself.