Making a noise-free DC-DC converter is very difficult. Any buck/boost style converter is going to introduce ripple and switching noise into the system. This is inherently unavoidable, and it’s very sensitive to the layout of the board. Actively or passively filtering out all this broadband frequency content is far from trivial, and there is no general solution - only a large, high dimensional tradeoff space.

You’re right that noise is a concern for any analog circuitry though, and if you want to, you can spend a lot of money on specialized DC/DC converter modules with integrated inductors that do their best to eliminate this noise.