You’re not wrong! My head hurts just reading through this thread!
When it became clear that the whole plot of Endgame would revolve around time travel, I have to confess I groaned... for precisely the reasons you mention here. If you’re entire premise isn’t about the time travel, and you’re just using it to solve plot issues, then things generally tend to get a bit sloppy.
But, as I’ve already said, I think the Russos were probably comfortable with the idea that some of the plot wouldn’t make sense, and they sacrificed a little logic for the right emotional beats, like Steve’s ending.
Can’t really say they were wrong to do that, can we!