Functionally, I don't think that's actually true. Squadrons continually do what they were always designed to do: provide a route for players to solo dungeons of a certain range. Using squadrons to level alternate jobs or clear ARR dungeons is still as effective now as it always was. Trusts can't be taken into earlier dungeons, so it's really not a continuation of the system as much as a completely new system that simply mirrors function. Squadrons also interact with the Grand Company system, which doesn't really carry forward into current expansion(s). Again, a separate system for a separate band of the leveling experience.