In my experience, the qualities of league teams in last few seasons have become close. So there are less high scorers. You should evaluate your scorer with comparison to league average, etc. Anyway 12 goals is not the worst. Some strikers can have good rating but really cannot score.

If your team plays really well, you may not need to worry about low scoring strikers. They may have other role to contribute. But if your team really need extra scoring ability, I am afraid it is hard to dramatically improve scoring ability of strikers, unless you assign him as free kicker or penalty taker. I will simply replace him and test another ST.