At the end of the day, DSP is a lot of math and a lot of hardware. A lot of GNU Radio's code is a monster unification of so many different choices into certain interfaces (or duplication of the same choices) for, presumably performance reasons? Or just keeping every single DSP technique ever in the God Library for the super power greybeard to use.

If you have a certain DSP goal in mind (say, RF comms), and you want to do stuff but not absolutely balls-to-the-walls processing (at that point, presumably you'd move to hardware), you can design your stack in fairly modular and composable ways. The field is pretty mature and the techniques just work.

In a software context, you can decompose the abstractions fairly cleanly. You won't get 5G high performance networking but you can get good enough results.