When did estimates turn into deadlines?

Working in smaller steps is how you should build software. Constantly get feedback and re-evaluate what you're working on with other members of the team. Instead of giving an estimate, use t-shirt size.

With constant feedback, the whole team is participating in the emergent complexity, instead of being passive and just annoying you with "is it done yet"?

but what if I’m working on something meaningful?

I can’t MVP my way to a simulation physics engine, when each feature or partial feature requires weeks of planning, testing, iterating and tweaking- privately, before anything can be delivered to be used.

Feedback, implies a working widget.

Agile pretty much throws out estimating anything bigger than a sprint. Even then, points don’t mean time and velocity can be wild for a mature team.

Feedback does not need to be on a MVP, it can be given before that from your fellow engineers. That said there are tasks which really take a lot of research before even fellow engineers can give feedback.

I don't need constant feedback, I mostly need to be left alone to do the actual work. Problem is, the Cult of Agile gets nervous by the third daily standup where you just say you're still working on the same thing, because everyone knows no programming activity ever takes more than a large t-shirt's worth of days, however many that is.