Based on the fact that we have fossil records and now understand genetics to the point that we can prove the path of evolution that led to humans and that all creatures on earth share a single-celled ancestor, I don't think it's reasonable to think that humans originated in something close to our current form off-planet. However, the idea of panspermia is interesting, that life on earth could've been seeded by building blocks that arrived via meteorite (or were intentionally placed by an intelligent alien species.) One of the questions that comes up when speculating on how common life is in the universe is that, as far as we can tell, life only arose on earth once. All life that exists and has ever existed, that we know of, share one common ancestor. If life were common where conditions were suitable, it seems we would've likely found evidence for multiple instances of genesis of life here on earth. Perhaps our planet was intentionally seeded with the right building blocks for life to form, or even with a cocktail of ingredients tailored to conditions on earth.

There are other smaller critiques that can be made toward your thought experiment, such as any craft that could crash into the earth with enough force to cause the mass extinction of the dinosaurs, yet remain structurally sound enough to allow for even a few of its passengers to survive, likely would be fairly easy to detect. Further, we have found evidence in the geological record that supports a meteorite coinciding with that mass extinction, in the form of a worldwide deposit of iridium from the meteorite as it burned on atmospheric entry (iridium is either extremely rare or non-existent naturally on earth.)

The stories in various cultures of gods with seemingly magic powers, or flying machines, or many other things that can be explained by technology rather than magic today is interesting, and I don't think it's entirely impossible that some could have been ancient aliens or members of some civilization that was technologically advanced far beyond our comprehension at the time, but popular culture and the "crank" nature of some of these ideas' most vocal proponents has understandably put most people with a professional reputation to protect off of these ideas. It's interesting to ponder, but I doubt we'll ever see any solid proof of any of it.

Some movies have touched on these ideas, Prometheus opened with a scene of an alien forerunner intentionally seeding a barren, early earth with the precursors to life. Mission to Mars also may be of interest to you, but I won't go into detail to avoid late-story spoilers. One of the Predator movies also showed a flashback to an earlier time when they visited earth and were received as gods. A relatively small part of the movie, but still cool to see it played out on screen. I'm sure there are many more sci-fi stories that explore these ideas, but those are a few relatively recent movies that come to mind that you may enjoy, even just for curiosity's sake.