Goku is definitely way more powerful than a Solar System buster. In the new movie Beerus sneezes and destroys a two stars on accident.
In BOG (Battle of Gods) a new untrained SSG (Super Saiyan God) Goku is 80% the strength of Beerus. We have to guess at how much of his power Beerus used to accidentally blow up two stars but I feel like because he was drowsy and this was an “accident” it isn’t too far fetched to think he used less than 1% of his power.
Now consider that SSG Goku is even more powerful in ROF (Revival of F). For simplicity’s sake let’s say he’s still at 80% of Beerus’ power though. Still, he can now go Super Saiyan in his SSG form. Traditionally SS multiplies a base power by 50 (the base power in this case being SSG).
So really Goku is leagues beyond “Solar System Buster”. I feel like Goku couldn’t destroy a galaxy which is billions of stars in one attack based on what we’ve seen but he could probably about get the job done given enough time.