I like the idea that time machines can only transport people within the time machines own timeline. You can go back in time and see yourself finish the time machine but you can’t go back one second before that.

Like it’s one end of wormhole that gets anchored at a particular point in time and the other end drifts forward through time, you can enter and exit the wormhole at any point in its worldline but only within that limit

It’s still allows for time travel, and explains why no one has ever met a time traveller.