The “eventually build dna base pairs” (that continue self replicating) is the uncertain and possibly ludicrously improbable step. See for instance https://www.nature.com/articles/s41598-020-58060-0 which argues for a probability per exoplanet small enough that it hasn’t happened a second time in the observable universe. On the other hand, one of the self-organizing proposals cited elsewhere in this thread may turn out to be correct and the probability may be much higher.

The point is that, while there are some cool ideas on the table, everything hinges on the particular value of this probability (not just a qualitative story of how life might have arisen) and we don’t know what it is. Still relevant: https://blogs.scientificamerican.com/cross-check/pssst-dont-...