That is to say: I seriously don't see any need for new note-taking software. If I want to take a note, I'll write it on paper. Or use one of MacOS's stickies. Or email it to myself. There are many other options, but those are the ones I actually use. If I wanted specialized note-taking software, I would have downloaded one of any number of free options ages ago.
My notes (on paper) are almost never just text, they're a haphazard mix of text, mathematical notation and ad hoc diagrams/graphs/flowcharts etc. If someone could design note taking software that worked for this style of note taking, I'd happily hand over my money.
A math-centric piece of software that allows you to write in equations via a stylus, then converts these to working equations. So, you write down the quadratic equation and can define in the software what a and b are, then solve for x.
There has to be something similar to this already.