That's actually really funny. Yes, indeed, in Star Trek lore, most of the major alpha and beta quadrant species are apparently related due to an ancient alien species being very lonely and deciding to seed a bunch of worlds. See TNG "The Chase." It's dumb. So very very dumb. So much so that none of the following series so much as play lip service to the idea.
Incidentally that aspect has nothing to do with the theory/hypothesis of Panspermia. Panspermia is the idea that genetic material could be transplanted from one place in the cosmos to another. The theory is talking more about meteors and meteor impacts. Unintentional transfer. It was a concern that one of the Apollo missions might bring something back with them. See, that part is totally plausible.
One idea was that an impact on Mars, nearly a billion years back, ejected basic organic material into space and it ended up on Earth, which is what kick started the big boom here. Though, most scientists don't think that idea really holds up and it's more likely that the natural conditions on Earth simply brought about the basic building blocks that lead to organic life to rise up and thrive.
What isn't plausible is pre-destined evolution, or having a species basically seed life a billion years ago, with any kind of nuanced intention, said species still being alive with relatively little change in their appearance. Which is what Prometheus and Covenant both want us to believe happened. Not only is that dumb, but it's wholly unnecessary.
