1. 100% agree. Tags based solution is non-started at scale. 2. Problem is pretty much all such apps today require you to be a methodical type-writer/curator on some system-of-record application. Hierarchical structures are only as great as your personal hygiene of maintaining them. 3. This is in no way a critique for Polar. I think its a novel effort but I believe we need something significantly better to be universally effective. 4. I am an aggressive user of Evernote and the best use I have gotten is type a keyword X in the global search and see what pops up from my personal knowledge graph. It's always this painful search (pull model of information) which only as good as your own hierarchy or note keeping or tagging. 5. Out of my own pain, I have started working on a project I called Kontext. Think of it as your personal knowledge graph in the cloud but you don't have to categorize or organize or tag anything. Just work as you would normally work with ideas in your head - clip, screenshot, comment, type thoughts and it would auto-categorize, auto-correlate for you with information push model when you need it based on your existing context. Another angle is temporal relevance is key; information relevance changes with time. 6. I am using some latest neuroscience research to base the idea on.
Happy to explore feedback, thoughts, use-cases collaboration ideas.