Turf War presents a whole new layer of strategy and depth that hasn't really been seen in the gaming world that much. Turf War itself rewards hiding, strategic covering and isn't completely ruled by taking bits of territory to win then being smushed with rules such as overtime... But Turf War instead puts the focus on the WHOLE Map, not the tidbits of strategic positioning. Turf War itself has a more competitive vibe to it due to its extraordinaire tactics involved and honestly feels the most balanced. Splat Zones if anything, is more likely to become favored by 1 set. In Splat Zones it really just comes down to who can keep the territory there and really just hold on to those strategic positions without getting killed in the process. It's usually not that fleshed out in terms of variety and feels more linear where your contributions are sparse and the only thing that matters is having an advantageous position to suit the strategic locations of the map. Whether that may be fun or not, it is still the same old shooter. What made Splatoon appealing was its fast paced ever-changing turf war that really demonstrated the concept of Splatoon in a way that made it exquisite in the world of shooters. I don't see Turf War being dismissed as a competitive mode in the near future, but it sure is fun and it definitely displays that strategy. Whether or not Aerosprays or Splattershot Jrs will dominate will mostly come down to if they can get a nerf (should target the ammo consumption) while rewarding long range weapons, and let's face it. Splatoon wasn't the most balanced game at the start. It's a new concept as a whole so we can expect a more balanced system in the near future (presumably August) then we can start talking long term competitive meta. Overall Turf War is what got us into Splatoon. Splat Zones is basically another other ordinary shooter king of the hill game just with more direct territory focus.
Turf War isn't a casual's type game, it's more than just that and if we give it the proper attention we can ensure a future for the Splatoon Meta than downright thinking ranked = competitive and fun = casual.