I quite like the new naval mechanics introduced by the 1.13 patch but the patch has definitely come with some growing pains. Some of it stems from bugs, but some it comes from QoL issues as well.
Requiring Marines to be in a separate army to join a naval invasion introduces needless busywork that mars the joy of setting up a successful naval invasion. A simple fix would be to simply have embarked armies with marines count marines towards the marines capacity limit instead of the normal battalion capacity until the number of marines exceed the marine capacity limit. That way you can simple have marines alongside normal battalions in a single army, and thus reduce the overall number of clicks you make. It would probably easier for players to actually use marines as well.
Reintroduce military shipyards would help the AI cope with the new naval changes. Condensing the shipyards into a single building has made life really difficult for the AI. From my experience, the ai seems to spend too much money on building ships, which really eats into their ability to build their economy. Separating the shipyard buildings will hopefully allow the AI to build up their clippers and steamer using buildings, such as ports, without increasing the amount of money they spend on ship building.
Speaking of the navy, I cant tell if the AI is really using their navies that well, or are building up their fleets well. I've fought multiple wars in my spain game against GB, and found that they were shipping massive number of troops to the Americas to fight my subjects. They kept doing that while I was launching massive naval invasions to occupy England.
In terms of the ships themselves, the AI seems to atleast try to make modern ships. The Free states of America for instance has a small navy of 51 ships, but alot of their ships are up to date, with even a few dreadnoughts. GB mostly has a mix of old and new cruisers + torpedo crafts. Italy, and Japan have a very disappointing amount of ships. None in the case of the latter.
Life in general seems really hard for the AI right now. Turkey, and Austria, for example, collapsed from the mid game onwards. Conveniently leaving room for Germany, and Italy to form up early, and start bullying their neighbors. France also fell to a fascist revolution and my subjects were experiencing lots of revolutions. I was fighting a near constant amount of revolutions post-1900s in my subjects, more so than in previous patches. The US also held onto slavery, forcing the North to secede and form their own union (with blackjack and hookers). Pedro got overthrown by a republican coup, and brazil still has the slave trade in 1934 alongside their American counterparts.