This is exactly how it feels!
It should not be like this.
If your coach is a super genius and your players are top of the league, you have to win 50+ games each season.
If not, the simulation is random. This is why I quit after FHM5.
It felt like I was wasting my time as GM doing all of this for nothing.
As for taking control as coach, who has 20 minutes of optimization time for each game of the season?
Once your lines change because of injuries, it's another 20 minutes to optimize for the next game.