Quick guide to help new players having issues hitting the ball straight.
Swing Editing in Options
The biggest issue many new and returning players will have is that the "Swing Speed" mechanic is fairly unforgiving at first. This option can be disabled or turned off in the Settings. Go to the "Difficulty" settings in the options and change the swing difficulty, or just disable Swing Speed.
It is also recommended to go to the training and "tune" your swing. This will help a little but ultimately going into the difficulty settings will result in the most drastic change to difficulty.
Remember that online ranked games will always default to the more difficult option, where the swing difficulty is Pro and swing speed is enabled.