The first major thing it could be is too many neurons / too many layers. The more neurons you add, and especially the more layers you add, the more generations you need for it to train. Once it does (eventually) get trained, it will perform better than one with less neurons, but the significantly longer training time might not be worth it. I just recreated your guy with the default 10 neurons in 1 hidden layer and am on 22% fitness by generation 100.
The other thing it could be that the creature is physically not adept at being able to jump or run due to its structure. I modified it as shown below and at generation 60 it's at 28% fitness
