idk man, sometimes i get this feeling too and i'm only 20, i don't think there's an age limit to enjoy any game, maybe you're just burned out from all of the hype around it in the last few weeks, the discussions here in the forums getting a bit heated every once in a while, maybe you've been playing a lot of footy games so another one just doesn't feel very exciting at the moment, i can't tell what's the big problem because i'm not you, but if i were you i would try having a good night of sleep and taking a few days off from footy gaming, both by not playing much and not thinking about it much, and then coming back to the demo with a more relaxed, rested and laid back mind, hopefully it helps.
Edit: Also, the lack of excitement from scoring may have something to do with the fact that goals don't really mean much for now because it's just a bunch of friendlies, maybe a master league can fix that, it just depends on how scoring in friendlies felt to you in previous pro evos i guess