Also, when I had a friend or two test the game out in later builds, they seemed to have difficulty to go as far as you did, so I didn't think there was any need to increase the difficulty in the end. But I totally see what you mean, cause I felt the same when testing the game over and over, but thought it was just me that got too used to the game mechanics, and knew how everything works of course.
I even asked if I should add difficulty levels with less or more spawning of obstacles, faster fire etc, but they told me it was already challenging and balanced enough, with the random situations appearing, and having good and bad runs overall (I should have listened to my gut tho haha)