Perhaps we understand panspermia differently. I understand it as a possible answer to the question: how did most of the life in the universe arrive where it is presently to be found? Clearly not all life, since as a matter of certainty abiogenesis has occurred at least once.

>> If surface abiogenesis is unlikely, panspermia is more unlikely because it needs the former, plus ...

That depends. Panspermia gets a huge multiplier from distributing the number of planets and eons on which abiogenesis might have happened just once. So it depends on the relative impacts of very different factors - neither of which have been well quantified.

If panspermia had ever been feasible, it was likely more so in the earlier universe. Personally, I prefer it because it seems to follow the Copernican Principle.