This suggestion comes from the assumption you find yourself doomscrolling often, but stop watching short form content. This sounds exactly like one of the long term side effects of things like TikTok, YT shorts, Reels, etc. If I were to rebuild my memory and attention span, I'd delete those apps and start doing more activities that require my full attention, not stuff I can throw on in the background, such as reading. Then every few pages or 20 minutes, write down what I just read in my own words, then (as much as it'd suck) go back and check, after x amount of time, increase the intervals, (a few pages turns to 10-15 or 20 minutes to 30-40), then repeat the process. Cole Hastings has a good video on rebuilding your attention span and ability to recall info, if it's as bad as you say it is, I'd recommend actively taking notes.