Kimi I think the avengers, specifically, don't quite know the effect they will be having on some of the timelines.
They also originally planned to go in and grab the stones without messing anything up, and putting them back an instant after they took them.
They couldn't plan on 2014 nebula accessing 2023 Nebula, which brought that universes Thanos and Gamora to them. This seems, on the surface, the most depressing of the changes they make.
2012 B, is now changed due to Loki escaping with the tesseract, so its unclear how depressing that reality would be.
We might find out in the Loki tv series?