>>715315451
You lack imagination, and planning. You assume faster than light travel is both necessary, and some determinate, distant point, and that scientific advancement is linear in all fields.
It could be very particular technology only really applicable to traveling vast distances in space. It could require such a great deal of energy that only a limited amount of resources, and personnel could be brought for a invasion force. They could have limited short distance travel afterwards, and have little, or outdated intel on life on Earth. They could have particular goals that limit a invasion forces efficacy, like wanting exotic meat, or as essentially a hunting trip of the rich ,and eccentric as opposed to a society's endeavor.
>>715316242
Another fine idea, why not two aliens. What if it's conscripts of a larger empire?
>>715316545
Ah yes, you know exactly how they work, and they wouldn't fall into the same design as every other piece of non-bespoke technology, being deliberately made to be operated by people who don't know how to make one?
>>715319282
You could only really get a good picture of how long it takes for a society to develop intelligent life, and select for sufficient intelligence to develop sufficient weapons technology to be a threat if it'd happened before.
Not to mention the huge jump between "Okay we're sending a group large enough to avoid inbreeding to put Ubungu in a cage, and start settling the planet." and being able to send a force large enough to challenge all the worlds militaries.
Ultimately the sort of thing being a spacefaring civilization gets you is more high level space war stuff, like having a tungsten rod fired at your ship's traveling speeds.
