I don't why this doesn't scroll the music staff smoothly, nor have a cursor clearly showing which note is currently being played, but as a result this is almost unusable for sight reading.

Jumps around way too much and god help anyone trying to use it that way if the tempo were to suddenly change or there are longer notes to play than the width of the screen can comfortably show at once.

This is why music is usually broken up into rows of a fixed width and the screen is scrolled vertically instead of being displayed as one continuously scrolling horizontal staff. It gives the eyes a reasonable buffer to work with.

I can’t possibly tell if this is worth it over leading class labeling tools in audacity. There is a sign up with no pricing and no mention of limits.

Why would i have a good impression if my first experience is a sunk-cost time-sink dark-pattern?

So disrespectful of your potential users time.

This just loads with the word processing displayed, nothing else