You can give all the caveats you like with 'again, i really love the concept' and 'thank you for making this' but at the end of the day you went out of your way to leave a lengthy negative review on something that is free you absolute total muppet.
I went out of my way to criticize something that I now care about, making me care about something is a plus but that doesn't mean it was great, I want to leave criticism to make anything else they do better. Assuming that the people that made this won't go on to do anything else would be depressing, I want everyone who made this to know what was good and bad about what they made for anything they work on in the future.