> 2. The overwhelming victory became Japanese Naval doctrine: the Japanese "learned" that if you sink the enemy's fleet, the enemy will surrender. This doctrine, Kantai Kessen, led to the Japanese strategy of WW2

Yeah, so the doctrine is known by another name: Mahanian doctrine, because it featured very heavily in Alfred Mahan's The Influence of Sea Power upon History, which predates Tsushima by 15 years. The general thesis of Mahan, at least insofar as it covers naval strategy, is that the general aim of the navy should be to seek a decisive battle to destroy the enemy's fleet and clear the seas of their ships, rather than a more Jeune École approach of avoiding decisive battle and instead focusing on commerce raiding.

It's true that the Japanese did fetishize the decisive battle doctrine to the point that it overshadowed over elements of Mahan's strategy (like, what you do after decisively beating the enemy's navy). And it's also true that the Battle of Tsushima was instrumental in forming Japanese naval doctrine for WW2.

> (aka: Sink the American fleet at Pearl Harbor. Because American carriers luckily escaped the Pearl Harbor attack, the Japanese would pursue Midway to continue to try to decisively sink the remainder of the fleet, again).

Now let's also point something out. The attack on Pearl Harbor was not Kantai Kessen. Its explicit strategic goal was to prevent the US from meaningfully responding to Japanese advances for the next 6-9 months, and as it turns out, the Battle of Midway was almost exactly 6 months after Pearl Harbor, and Guadalcanal starts almost exactly 9 months after Pearl Harbor. It was not intended to be the supreme destruction of the enemy's fleet that Kantai Kessen was--it was at best a weakening of the enemy that would improve Japan's odds of the final Kantai Kessen, not the main event.

The attack on Midway was intended to be Kantai Kessen, but the actual battle was not. The Japanese goal was to occupy Midway, which it thought would enrage the US enough to come out with its full navy (following Mahanian doctrine, like Japan was) to contest it, at which point the Japanese navy would be victorious and crush the navy. American foreknowledge of the strike allowed US carriers to surprise and sink several carriers to the utter horror of the Japanese, but it was still not seen as the decisive battle effort.

The closest the Japanese got in WW2 to their actual Kantai Kessen plan was the Battle of Leyte Gulf, which was launched in a hope of actually forcing the decisive battle they craved, although from a position of pretty clear weakness. The actual battle went quite badly for the Japanese, with the Japanese withdrawing from the engagement at the Battle off Samar (suffering arguably greater losses) where the Americans were hopelessly outnumbered.

Talking about the Pacific theater in WW2 is hampered by the fact that, in retrospect, the importance and influence of aircraft carriers is undeniable. However, most naval officers at the time still believed in the supremacy of battleships, and the carrier engagements would have often been seen as sideshow engagements to the main course of the battleship engagement yet to come.

> 3. The world watched the battle, and learned that bigger-guns were better.

I'd use 'confirmed' rather than 'learned' here. The general thinking even before the Battle of Tsushima among the British Navy was to move to a more uniform gun caliber, and this was partially driven by the need for simplified logistics that would come about with such an effort. Even without the Battle of Tsushima, HMS Dreadnought would probably have had the same loadout that it had in our timeline, so I'm not sure that it's entirely fair to attribute dreadnoughts to Tsushima.

> 4. The Battle of Tsushima was the last time ships lined up and attacked each other with their guns in a blaze of glory.

This is just plain false. Both the Battle of Jutland and the Battle of Surigao Strait feature textbook battleship lines engaging on each other in a crossing-the-T maneuver. The Second Naval Battle of Guadalcanal involved battleships engaging each other. There were a few pitched battles in the Mediterranean in WW2, whose names escape me, one of which even involved an aircraft carrier trying to fight in the line of battle. There's even more engagements involving just one or two battleships that you might struggle to count as "ships lined up and attacked each other," so I'll omit those, but Wikipedia has a list here: https://en.wikipedia.org/wiki/List_of_naval_battles_between_...