I actually played just one round and managed to beat it first try, so I can't comment on how frustrating it would be to start over (yet). I think the fact it's beatable at all first try at all is a testament to how readily it can be picked up, though. I did wonder if there was a separate action to "collapse" a quantum state (as opposed to simply picking a number for it to become), but ultimately that didn't trip me up in the end.
I think this could be really good on mobile! A daily Quantum Sudoku would probably scratch the same sort of itch as Wordle, and I really do like that the interface eliminates obviously impossible options - it feels more casual than pen-and-paper Sudoku even if there is the possibility of collapsing a cell prematurely. Plus, if it's a daily puzzle, I'm not sure there's much call to play for more than a few minutes. The ability to play/replay previous days would certainly be welcome, though!