I still really don't get the Cap timeline part. Really seems to be like a nice ending they wanted to give him without caring about how it affected their established time travel philosophy.
Like, if he went back and lived a whole life up until the pt he was on that bench, then everything he brought back with him is also in that same timeline. How is that 'alternate'? Unless he, once he was finally old, decided to travel back to the alternate universe, in which case theres a lot more gaps that need to be filled in about how he can now hop dimensions, not just timelines. It's all really just hand waved away for the purpose of a cute ending.
Like, if he went back and lived a whole life up until the pt he was on that bench, then everything he brought back with him is also in that same timeline. How is that 'alternate'? Unless he, once he was finally old, decided to travel back to the alternate universe, in which case theres a lot more gaps that need to be filled in about how he can now hop dimensions, not just timelines. It's all really just hand waved away for the purpose of a cute ending.