I think fleet arena has always been prett RNG-dependent, comparatively. A lot of that is because there are relatively few ships, so most people wind up running pretty similar fleets. Once you’ve reached a certain power level, the only determining factor between two fleets is who gets better RNG.
If they intend to change that, they can’t just go on releasing new meta-defining ships every few months. Everybody will change their fleet to take advantage as soon as possible, and it’s back to an RNG-fest. What they need to do is release enough ships (including new capital ships) that take advantage of new factional synergies, so that there’s a meaningful difference in feel between running a Republic, a Rebel, or an Empire fleet (or, dare I say it, a Sith, Separatist, or Resistance fleet). And at any given time, at least three of those choices need to be competing to be the meta.