I can't think of any better way to halt a metagame's progress than to never play more than one game mode. Splat Zones is the simplest gametype from a strategic perspective, because it's both the simplest objective and the most straightforward to win (take point, set up, hold point, as compared to towers, where you need to work with and account for a lot more variables). This is not a bad thing. It just means that it's the gametype that everyone is going to be most comfortable with, since we learned ranked with it and have plenty of experience with it.
If you enforce zones only in competitive, you force the metagame to develop around lightning pushes (where you wipe the enemy team as quickly as possible) and defensive setups (where you try to get into safe positions and block the other team's fast push). The team with the best defence wins, because zooka is so strong that it's almost certainly going to work at some point.
Hopefully you see the problem already, but if not, I'll elaborate further.
Now examine tower control. Instead of being all about single, all-in pushes into defensive setups, TC is about protracted, standoff pushes at multiple areas of the map, with a forced positioning disadvantage and protecting against waves of defenders.
The problem with limiting gametypes, especially this early on, is that you are gambling on your understanding of the gametype being correct, and for a gametype like towers (which is relatively new and very poor for non-organised play) or rainmaker (which isn't even out yet), I don't believe this is actually possible.
Naturally, I've been arguing against turf war for months now, and this might seem like a contradiction. Turf is not like the other modes in that it's timed, and the only thing that matters is how the map lies at the end of the game. I believe this is a fundamental problem, but I also believe that playing competitive turf is the only way to demonstrate this gametype's problems. I would prefer turf to be out of the rotation as soon as possible, but I also want people to acknowledge that it's bad instead of constantly having that question mark over their heads.
Now, returning to my original point.
Multiple gametypes require mastery of the game, and enforcing single gametype means that a team can win a tournament without being the best at the game.
"but items/coins/bonus in melee!" No. Stop comparing to melee, it's a fourteen-year-old party game made competitive by sheer fluke and popularity, whereas Splatoon is new, has much less leeway for people to make idiotic decisions about its competitive future, and is at least designed around the idea that it will be played competitively. Items add needless randomness and break the game in a way that is not ideal. Other gametypes in Splatoon require that teams be good at more than just using zooka, getting four kills, and then throwing down splash walls and putting chargers on choke points for 50 seconds. If anything, zones is looking to be one of the shallower gametypes, at least as far as team compositions go.
Even if the comparison were valid, items and coins were both accepted gametypes in the very early days of melee and were demonstrated to be trash. The community, splintered though it was, did experiment with these gametypes and determined them to be bad. Likewise, the other various gametypes in CS:GO were experimented with in the CS1.6 days until demolition was decided upon. CTF and Deathmatch are both still played in Quake 4v4. Halo actively runs at least five gametypes (Team Slayer, Oddball, KOTH, Neutral Bomb, CTF). Competitive TF2 runs KOTH and CP, only now beginning to phase KOTH out of the rotation. At no point did people say "well I played this one time and didn't like it, we should ban it".
Maybe, eventually, we can start to discuss removing modes from competitive play. But we need to know how they are played before we can do that. I've seen at least two games ruined by communities that didn't know a ****ing thing about the game they played and refused to play with rules that were not what they were used to, and restricting competitive to Zones this early on would almost certainly make the trifecta.
