This is not remotely a safe assumption. We know interstellar travel is resource intensive, but it's within the capabilities of todays technology. It was probably doable with some effort with 1960s technology.
This is the same basic error of reasoning where people say because the moon landing happened, faking the moon landing was also possible (it wasn't: video editing technology of sufficient capability did not exist - space flight and CGI are two entirely separate lines of technical problem solving).
It’s not within today’s technology to actually visit an extrasolar planet. We could possibly do a flyby with a solar sail but we don’t have a way to slow down and enter the planet’s atmosphere. And even that only gets us to the relatively small number of stars that are in our immediate vicinity in any kind of human-civilization-scale timeframe.
This is the same basic error of reasoning where people say because the moon landing happened, faking the moon landing was also possible (it wasn't: video editing technology of sufficient capability did not exist - space flight and CGI are two entirely separate lines of technical problem solving).