You must be pulling background from the books because I haven't seen anything in regards to Rhaenys that tells me she would hold back if she had a winnable shot at the throne. Her asking the Queen if she hadn't thought of herself on the throne was done in a way you could tell she had absolutely seen herself there.
Take that person and give her the opportunity to take out half the people with claims and have a justifiable excuse for it plus a war is inevitable that will put the lives of her granddaughters in danger? Don't tell me she doesn't pull that trigger. The fact that her own life was in danger only hours before if she doesn't bend the knee gives her a self-preservation reason and she is not the kind of person that goes down without a fight.
I absolutely reject your analysis with extreme prejudice.