IF time travel can be invented it already has been

This is just pure logic. "If time travel can be invented it has likely been invented by an intelligent species millions or billions of years ago already."

So, if time travel is possible and joined with space travel, travel to ANY location or time would be instantaneous.

Logically speaking then: "IF time travel can be invented it already was invented millions or billions of years ago on another planet or dimension or galaxy".

Also, if time travel was invented it is also here, and always has been here and will be here too since before this planet even existed in time and space.