I know normal Infantry did most of the work on D-Day. My post was more a tongue in cheek indication that it was not only the US who had marines and multiple countries were involved in D-Day

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Yes, D-Day wasn't a US operation. Hollywood please note
My point is just to set the record straight from earlier that the Allies didn't need to bother with marines at D-Day because the USMC weren't there. But nor were the Royal Marines in large numbers. I would argue this is because the operation used other special/elite forces, British commandos, US Rangers and British and US airborne. Paras/gliders were not really possible in the Pacific, and gliders can't be launched from bases too far away from their destination.
Budding HOI4 commanders of the three great naval powers can mix their forces, depending on the operation. There is very little additional cost to create some marine formations, taken overall, especially if you don't create them at full Div strength. And Japan even gets Marines already researched and an SNLF unit built when the game starts.
Special forces can be used in other operations, and can be mixed with infantry, even tanks. It was done IRL and can be done in HOI4.
One other issue that might be interesting to look at, given this issue of the greater org of marines. All three countries used their marines as garrison forces for protecting their naval bases. They might be very useful to defend a few of your most vulnerable ports from invasion. Expensive garrisons, but if it prevents losing Hawaii, Truk or Singapore, then it might be worth it.