I'm not saying it was bad.
DC, at the time had very little interest in the JSA.
The mini-series was really well written and drawn, but it was something DC 'was just putting out'. It was more like a 'try-out book' for the creators to keep them busy and not let them wander off.
The JSA was probably chosen because it would have the least impact (ha, pun) on the then current DCU and could be unrelated to anything else while still showing off the creators' abilities with superheroes.