But the RN used armored decks, which seemed stupid at first (slower speed), but which later proved to be very useful against Kamikaze fighters.

We had a few, but we didn't need all that many while fighting in Europe. But the Royal Navy's carriers were far more advanced than the American ones.

And hell, look on a modern carrier and you'll have a hard time finding something innovative and vital that was invented in Britain.

My point was missed.  I acknowledge the British contributions to carrier technology (and tactics - remember, the raid on Taranto helped cement the tactics used in by the Japanese in Pearl Harbor).  My point is that the only two countries that developed the carrier into the decisive weapon were Japan and the US - and if truth be told, the Japanese grasped the concept of the carrier based task force a lot quicker than the US did.  In hindsight, the reason the US  had to develop their carriers was that their battleships had been disabled at Pearl, otherwise, it was very much a "battleship navy" mentality at the time.

Although there were important battleship duels in the Pacific, these were few and overshadowed by the carrier battles.

As Woody says, the overall battle stratgy of the British was not towards the large fleet carriers, but more towards smaller striking forces in support of landings, and the invaluable anti-submarine operations of the North Atlantic.

As noted, the British developed the steam catapult, the angled deck, and then they took it all away with the Harrier!!

That's is but part of the reason the UK was taking a beating on the Asian front, unlike WWI where the overseas threat wasn't so extensive (it was the German colonies that fared the worst). To look at it, the carrier forces were more offensive than defensive over a greater expanse of ocean. The UK's 'invading' nature had fairly well subsided by the beginning of the 1900's while Japan, on the other hand, was full throttle in its invade/occupy phase.
Even prior to the Pearl Harbor attack, the USN wasn't on par with the IJN. As in WWI -- where it 1st maintained an 'isolationist attitude' -- the US had to play catch-up. There, of course, was the basis for the Yamamoto statement, "I fear all we've done...is to awaken a sleeping giant."
When the US formally declared war in WWI, it still took a long while to train troops and prepare supplies (much of the machinery promised wasn't ready even at war's end).
It may seem like the US, if no one else, should have learned from the 1st time but it, too, wasn't faced with the invade/occupy situation until made necessary in the WW2 Pacific.