Pointing out flaws IS constructive criticism. This happens all the time and it bugs me:
person A comes up with an idea person B gives good reasons why it's flawed person A - the one who wants to innovate - says that fixing those flaws isn't his problem, and that person B should fix them.
WRONG.
The person who generates an idea, the person who wants to do something new, is the one who is responsible for brainstorming, finding problems, finding solutions, and pivoting as needed.
To say "your criticisms should be bundled with solutions" just raises the bar on criticism, and when it costs more to generate criticism, you get less of it.
We should all encourage criticism, and then we should make finding solutions OUR problem.
I much prefer someone to criticize my work, rather than sitting quiet just because they can't think of improvements. After all, I'm probably much more likely to come up with a solution than they are, and the reason I didn't is just because I didn't think of that problem.
In the end, I judged that (valid) criticism is better than no criticism, despite the negative feeling of being the guy that just "tears it down".
Also, maybe you could make your feedback constructive by providing ideas, alternatives and suggestions instead of just ripping it apart but adding no value or solid suggestions beyond that.
The point here is much bigger and more significant than any of your individual criticisms.
The point is this - these people are rethinking the problem of notation, and redesigning it from the ground up.
I think their approach is totally badass, and I love the fact that someone is tackling this!