Facing a very similar issue and trying similar things unsuccessfully, I've found out lately with my coach that a more promising way to break out of the cycle of "wasting time" and beating myself up over it might be very counter-intuitive: Self-acceptance.

I've found that acknowledging my need for relaxation and satisfying my curiosity was a solid first step in helping cure my addiction on a more fundamental level.

Changing my own internal reaction to realizing I spent the last 30 minutes on Reddit from self-punishment to "Oh, interesting. Looks like I needed a bit of a pressure vent from the complex work I'm doing. I'm worth that. Is there anything even better I could do to myself so I can relax more effectively with quality time off?" at least to me was a way better way to deal with it.

I wouldn't say I'm "cured", but I spend way less time with these things, more time I would define qualitatively highly (like playing some piano, walking or just dozing a few minutes).

Stopping the internal conflict from the other end might be worth a try for you too, even if it sounds weird.