I could possibly buy aliens visiting etc, on a long enough time scale humanity could colonize the galaxy without ftl drives. I want to believe but there's too m

I could possibly buy aliens visiting etc, on a long enough time scale humanity could colonize the galaxy without ftl drives. I want to believe but there's too many holes. One of the biggest is Gruschs claim that there's 12 or more captured space craft that have crashed etc and we have alien specimens.... Are you telling me an advanced civ that builds hardy interstellar spacecraft made it here with 12 vehicles or many more but managed to crash 12 of them and not recover the wreckage? Doesn't seem that well planned for a kardashev 2 to 3 civilization.