The future causing itself to exist in fiction; huge plothole?

[Maze1125]

You have clearly never studied formal logic, because it works perfectly in logic.

The future can't exist without the past surviving. Future us would've already been back at this point.

Yes, exactly, a stable loop.
Whichever event you consider, it appears that the other event has already happened first; but that's not inconsistent, merely potentially confusing.