I don't know if all my comments will be satisfactory since I can only base them off the 2 level demo, but I will say them anyway.
The first thing to note is how the gameplay structure has changed. Instead of getting from point A to B in order to beat the one level of the game, you now collect all the infected crystals of a level to beat it and go onto the next. While this is unique from the standard racing game formula, it is not quite executed well.
The main problem is with how inconsistent the gameplay is paced in the demo. Sometimes you will have 1 or a few undead rods chasing you with not many ways to shake them, sometimes you will be ignoring/attacking them once you have the shield powerup, and sometimes there are no rods in sight and it's just pure fxx collector, for lack of better wording.
In the demo, nitro is way too situational. They are in dedicated spots, and you can only use each nitro once upon pickup. They could be changed so that a nitro can be stored in an inventory for that level so you can use them later for evading rods, making them way less situational.
My final comment relates to the OG fxx runner. The gameplay of that game was pretty unique as well, and like the new gameplay style, I feel like it has not reached its full potential. Maybe along with the new levels, there could be levels where you have to get to a huge infected crystal to destroy it while being continuously chased by rods.