1. Unsubscribe. From everything you haven’t read in the past year or so. This obviously has compounding benefits, assuming you refrain from further subscriptions.
2. Delete. Flag what you need to save and delete everything else (or vice versa, filter and delete anything you don’t need). A fully clean inbox/browser will provide daily motivation to keep it clean.
3. Review all your bookmarks/tabs, etc and identify 10-20 general themes. What are you interested in? Can you start an activity or program that would allow you to review some of your favorited content in a more organic fashion?
To-do lists can be off-putting, and I doubt you would ever sit down to read through hundreds of webpages in abstraction. By applying it to a project or educational program, you will have a tangible product/outcome, and find that you don’t need as many bookmarks on that topic. (Or maybe you’ll create more.. at least, they’ll be different).
Whenever I do this, I find myself deleting about 10% of bookmarks with every new project (and adding back less than that).