I played for a bit on my PC, and manager-style games aren't my usual go-to, so take this with a grain of salt.
1- I like the consistent style overal, but sometimes you have different pixel sizes and that stands out. The ball, the net in the goal and the lines separating the spotlights in the stadium are the ones more noticeable, clashing with the rest of the graphics.
2- The defense mini-game feels substantially easier than the attack mini-game. Perhaps making the goal taller could balance both out: making the defense more challenging and the attack easier.
3- When I went to jump in the bath with the boys, I thought I had to mash to run. The manager already runs automatically it seems, and add that to the mouse clicks, he ended up flying to the stratosphere. I wonder if tapping to run is really necessary. I didn't play another match to test this out.
4- I found there was too much idle time during the "action" parts of the game. In the golf/attack mini-games, after you hit the ball there is a lot of time until the game proceeds. It's a bit concerning during the attack mini-game where you are under a time limit.
These are my thoughts on the demo. There is some good stuff in there, so please don't let my feedback discourage you!