I think it's worth stating that XIV is not XI. They are two completely different games with completely different player environments. Just because people are asking for more agency back into the game generally speaking does not mean the alternative is FFXI meta. That is a leap in design on a galactic scale with plenty of planets in between, many of which can sit comfortably within a goldilocks zone of balance, approachability, and depth.
In regards to trees specifically, there are absolutely ways that FFXIV could introduce some semblance of skill trees. I don't think it's mandatory, but it's very plausible. There are too many possible ways an idea can be approached. It's silly to suggest that it's not possible for any of the literal billions of possibilities to be viable and balanced.