Going back in time to warn my past self not to meddle with time travel.
Maybe they have and they did and it worked. If they hadn't, things would be far worse.
Try out "Travelers" with Eric McCormack; non-warning strategy. Pretty decent and has Eric in a more serious role. It was a three-and-done from Netflix, I believe.
Stephen Universe has the most realistic depiction of time travel I've ever seen. Stephen goes back to try and solve a problem, makes everything worse, causes endless versions of himself to appear and fight one another until all but one of them is dead, and nothing appreciably changes.
Time travel, buy one of the big stocks early, reinvest all the money in social housing, education, and environmental projects. When you run out of money, time travel back again and buy a different big stock. Repeat until wealth is sufficiently redistributed. Temporal Marxism.
The sheeple theory of timeline consistency
I list that fantasy in the same column as the notion that a dedicated journalist could reveal something awful about a politician that would kill their political career. Thinking a lot lately about how wrong Transmetropolitan was about Spider Jerusalem's influence.
If only someone had warned us about climate change decades ago!
I might not trust anyone else about the future, but I think I'd believe a future version of myself warning me about something in my own future. At least that's what I've resolved myself to do if I ever were to time travel to the past myself, so I also try to be ready for the arrival of a future me.