Correct. So how is that confusing?
Nah, that doesn't really work. You get paradoxes that way. The whole "travel back in time, kill yourself, now you never can live to travel through time, which means you never actually killed yourself, which means you DO travel through time," etc. Unless you travel back in time and literally do nothing but observe and don't manipulate anything a single timeline always either remains unchanged or makes a neverending circle.
T1 had the neverending circle which made it the most elegant and never in need of a sequel--ever. But now that we have both sides trying to manipulate the past every new damn movie you either have a series of five hamster wheels or you need a non-endless loop way of them resolving things, which is where the alternate universes come in. If you think those concepts are too "stupid" then you really should just not watch time travel movies or stick to ones like Back to the Future that don't even try to be remotely logical.