Life went from minutes per generation to a year per generation!
Mutation rates of RNA-based life was likely 1,000x higher than later DNA based life!
How are these “not relevant”?
It’s like estimating the velocity of a ball from a replay that has slow mo, time-lapse, and the game being played changes!
Intelligent life on earth is DNA/RNA based, not one or the other. If you take the mean rate your interpolation from now back the origin of such life with that particular mean rate of numerical growth in base pairs holds with error margins.
https://en.wikipedia.org/wiki/RNA_world
Your assumptions are faulty.