Steam catapults are superior.
That's all there is to be said---there's no reloading except for cranking the thing back to position, there's no smoke, and no silly FLAMES on a warship (Come on now, don't you people learn ANYTHING about naval warfare? You do NOT start fires voluntarily around aircraft loaded with ship-killing ordinance).
Renaming it to "repressurisation" doesn't stop it from being reloading, and sticking a solid rocket-fuel pod into a slot is not worse than monitoring a pressure reading to ensure that the valves don't fail and make something explode. Using liquid hydrogen and oxygen would have their share of issues, but would be completely clean, powerful, and potentially restocked using electrical power. Or we could use a railgun, I mean, if we are not aiming for 2000+metres per second then we can tone down the power requirements and use pulses or something... Mostly though, rockets are local, while the steam has to be shipped in from somewhere, which is a lot of volume and points of failure. Last thing you want is for your catapult to be out of action for hours while you try to track down a loose bolt somewhere.
Not to mention that a steam system needs to be sealed, so you are pretty much stuck with cranking it back after every launch. Rockets and rails on the other hand can run serially if you have multiple harnesses.
Replacing smoke with steam is not that big of an improvement. The steam we are talking is probably at a rather extreme temperature, also it is at sea, so it'll absorb salt from the environment. Salty steam is not fantastically nice. And it is entirely possible to make a rocket that produces steam as its only exhaust. Certainly steam is less offensive than smoke, but it is not free of problems. A railgun on the other hand would have no exhaust at all.
Incendiary ammunition is not some sort of automatic win condition for naval warfare. Most military-grade explosives are about as flammable as people are or can often burn to ash without exploding. Also, hot steam can start fires too... Electricity can be a problem if it makes contact with a detonator, but those ought to be insulated...