Arguments on why subs are really just not cool
1) they depress siege turnout: in areas like Indian ocean and med the threat of subs means dreads and cruisers are rarer.

Various tines in GNE and Japan sieges were avoided as three subs working together can easily sink all surface ships moving through chokepoints or in general. The argument for weak planes is they are small up to 500 blockish so it shudnt sink a dread. Subs are small and can ez sink dread.

2) skill/fun/gameplay-
Enjoyment and dopamine hits come from manoeuvring and firing. You are rewarded for both and therefore ship v ship is always fun as each ship has unique advantages that can be countered.

A destroyer has speed and torps, it can easily cripple a dread, but a dreads gun can do the same. Though the dread has an advantage in power, it requires skill to disable the destroyer.

This simply isn't the case for subs, it's incredibly frustrating to be sunk by a sub or damaged awfully and not be able to partake in a siege. The dopamine hits are one sided. All ships should be able to counter the sub.

3) subs are too fast -
Subs don't even need to be used strategically, being used faster than dreads make then really op. Most times they can avoid being sunk by running. Essentially the skill used is a variant of ramming.

How would combat evolve without subs...

1) more varied fleets-
The reduction in need to have a destroyer screen around Dreads or carriers would mean u can finally split fleets into squadrons. E.g. you could have a cruiser destroyer sqn as a scouting force to relay back to dreads.

We could evolve tactics in open water without worrying about being sunk.

2) the possibility of fun battles being ruined by subs is gone.

Essentially, it's not fun to fight an enemy you literally cannot win against unless you have a very specific type of ship causing huddles of botes. It's not even viable for Japan to take Indian same way it wasn't for Nordic to take pacific due to the threat of subs.
If subs were to disappear or be heavily nerfed for a few weeks, the rate of fleet combat and scale would increase. The reason no one took pacific was due to submarines and getting stuck, the same reason why the Indian ocean is unfair and really biased towards nations not in the pacific area.

Submarines are not fun for anyone apart for the sub pilot, they can destroy ships with a single salvo, are immune to ships apart from one. They can easily run away and losing a submarine means nothing. By removing them we can finally develop tactics on the open water, it also means smaller fleets aren't forced into halving their firepower due to needs for a destroyer.