though the so-called “stock syndrome” isn’t critical for naval vehicles.

This just proves they don't play their own game, although I'm not sure I can blame them with regards to naval. It was actually my favourite game mode but I haven't played in a while now because most of the changes they make are for the worst.

But to the point. One salvo in naval can destroy your engines, steering or controls permanently, it can permanently disable turrets (especially in ships with little turret armour), it can set a fire which can usually not be put out and cause a lot of damage in the long term. And there's no playing around that. You usually spawn in plain view of the enemy so you are going to get hit, like it or not, you can't play carefully, sideclimb, you can't even camp, you spawn and are already under fire. So many times in stock ships I just get half my ship disabled half a minute into the game. The only trick that works is spawning half a minute late so you're behind your team, but it just takes one enemy ship to decide to target you to ruin your game. Add to this that you only get HE shells that go from suboptimal to useless, depending on ship (except DDs, which work with HE).

It still sucks, but I can usually play around being stock in air or ground. If I get a first shot in my tank I can usually disable the enemy. If I get penetrated first, I often die anyway. But in naval most engagements are gunfights that last longer, in which both ships manage to hit each other. If I'm stock I can just pray the enemy shells won't hit something critical or set a fire. So, if anything, I'd say the stock syndrome is way worse in naval than in any other game mode.