I would argue if “high level design decisions” are getting in the way of coding, this is a sign of over-design or premature abstraction. If you write sufficiently loosely-coupled code, it’s not hard to re-organize later.
You can't loosely couple around questions like these most of the time, at last not without excessive abstraction.
For "how do I structure this reasonably isolated 0-1kLOC component", I agree, easy to fix later if needed.
And like for example if you want to change web frameworks, that's something you can do incrementally. If you're talking about front-end, just find a way to encapsulate your old code behind a clean interface and start implementing new components in the new framework. If you're talking about back-end, then you can just implement new endpoints in a new language if you want even, and gradually migrate things over when you have to modify them.