Yes, there is still a last bastion of focus, productivity and anti-distraction. It's the terminal, which is why I find myself using TUI apps more and more as time goes on.
There are specifically a few principles we need to preserve to prevent the marketers from ever getting a foothold in the terminal. They are: general computing, text-based UI, and composability.
What that means is we need control over which programs we can run, we need to work with programs that view/input/output primarily text, and with programs that are modular (so that if a marketer injects their filth we can run it through grep and strip the filth out).
In other words, our modern needs are not much different from the old UNIX philosophy.
That is the technical remedy. From a sociocultural standpoint, though, the best way to avoid advertising is simply to be esoteric. Be interested in weird stuff which is too small to attract the interest of marketers and their filth.