Firstly I want to say that you really have nothing to apologise for. Like you say, puzzle games are a tricky one and i'm certainly not a 'puzzler' so there's a very good chance that this is a me issue and not a you issue!
The CRT thing is really minor, but just a thought I had as I have entered some more retro jams and it usually involves trying to recreate older systems, so I come across those shaders often! It's not a big deal and a super easy fix / addition if you use a similar effect in the future and feel it might affect readability or accessibility.
I was going for the right hand side of the board as that was I think the ending I wanted? But honestly don't sweat it if I'm an outlier on the difficulty, I wanted to give you an honest appraisal of my feelings, but I don't believe it's actually a negative part of your game.
I really do think you should be very proud, it's an excellent game, just not something I'm all that good at haha.