I show off my anger after Jags losses. I can't help myself.

I disagree.

By 1947, humanity had already developed nuclear power. Since then we've failed to develop fusion power.  We have developed fusion weapons, but these were conceptualized before 1947.

By 1947, humanity had already developed rocketry at the V-2 stage. In the last 50 years rocketry hasn't progressed any faster than automobile development did in it's first fifty years. We don't have anti-gravity, nuclear engines, or any propulsion system even close to the requirements for interstellar travel.

Likewise, we've only made normal incremental developments in the jet airplane technology developed during WW2 (before 1947).

Genetic engineering is a big part of the tech advance, but it has really only become a factor in the last ten to twenty years.

The transistor was also invented before 1947, although the first successful one was built shortly after Roswell. Still, I doubt an alien race capable of interstellar travel would use transistor technology large enough for humanity to discover and reverse engineer. Right now we put a billion transistors on a single silicon wafer. Maybe a case could be made for alien-tech computer development, but that's the only technology that really took off shortly after Roswell.

A race capable of interstellar travel would choose to expand to fill the galaxy. I don't see how any race could develop without at least some biological need to procreate and expand. A race would have little reason to avoid colonizing habitable planets without intelligent life. Why would they not colonize Earth? One explanation is that the aliens would find Earth unsuitable. If that's the case, it's unlikely they would show up in Roswell in a relatively human-looking spacecraft. Another is that they refused to colonize a planet with intelligent life. If intelligence is very rare, the odds are very much against the only other intelligent race in the galaxy appearing in the short time that humans have walked the Earth. If intelligence is more likely, then the first intelligent creatures would have appeared much earlier. Only one intelligent interstellar race will rule the galaxy. That one race must have been willing to wipe out, or at least suppress, all competition, yet leave humanity alone.

The alternative explanation that we were planted here (possibly as a colony) doesn't fly when you compare our DNA to that of other Earth animals. We clearly are genetically related to species that existed on Earth over a hundred million year ago. If life on earth was planted, it was planted nearly a billion years ago. For this explanation to work, it follows that an extraterrestrial race must have ruled the galaxy for nearly a billion years. If so, they've done an amazing job of covering up a billion years of evidence of their existence, only to blow it all by crashing a spacecraft in Roswell. It's much more likely that all of existence is just my dream, or someone else's computer program.

In any case, we would see some spectral evidence of extraterrestrial energy use in nearby star systems. It's unlikely that all of the nearby star systems are unsuitable for colonization.