I really loved StumbleUpon, but I fear reviving it would lead to nothing but inorganic traffic and malware.
That said, it would work. Whether it would be financially viable is another matter, but going for profitability is ruining a lot of fun.
People seem to have forgotten StumbleUpon had a pretty decent configuration page where you had to manually select what topics you were interested in, and that submitting new pages wasn't as simple as just submitting the URL. On top of that, I'm pretty sure I remember a "block this domain" option if you clicked the arrow next to the thumbs down: https://i.sstatic.net/VLS4c.png