Is the learning curve too steep to get into? - well there's no proper tutorial and no area one can practice.
Is ship balance preventing you from playing? - no idea really I don't play GSF much to begin with so I cannot comment on this.
Are you not playing because you feel GSF needs something new to bring you back in? - from want I've seen yes, it NEEDS new maps (the galaxy is a very big place), modes (different types of matches, maybe even solo/group content vs NPCs), new items and cosmetics and new Ships definitely (Zakuul designed ships would be nice).
Matchmaking issues? - only problem I see is the amount of people doing GSF is greater on one faction then the other
The fact that GSF is character based and not Legacy? - this could do with parts of it being legacy like the currency and cosmetics but I think everything else should be character based