You're comparing apples to oranges. Raindrop doesn't need to be installed (on desktop, different thing if you want to use their app on mobile). And it lets you categorize your stuff in folders _and_ tags and give each of them a representative icon. I've using this as a complement to the 'Saved' feature of Feedly and frankly despite the web ui being a little clunky it works really great.
All those are simple to set up in Notion. Both run via web app and can include categories, tags and additional information. They certainly target different audiences, but in my experience Notion isn't missing anything Raindrop has, it just adds more functionality. Raindrop works well, no doubt. It just doesn't add much functionality to browser based bookmarking.