Be glad you can’t if you are referring to PVP. I am just thinking Normandy with a bunch of swimmers getting headshot by one musket.
True about the doors, although to be fair, WoW to this day has no openable doors or hatchways. Zero. I’ve told WoW players that and they swear I’m lying. I kid them not. Check it out sometime. All the cities, all towns, all the dungeons have nothing but openings in buildings. No doors ever swing, or open or close in that game. Which in my opinion only makes it all the more cartoonish and silly.
But I agree, this game in 2021 should 100% have opening and closing doors!
Even Skyrim has them. Heck, Oblivion has them and that game is over 15 years old.
you dont want them to develop a new feature which will create bazillion new bugs do you?
you don’t want them to develop a new feature which will create bazillion new bugs do you?
they’ve been creating a bazillion new bugs without adding new features…maybe new stuff will fix a bazillion bugs? /s
Also only witches can float.
Dungeons have doors. They’ll open , but never close 
Not enough budget, please understand
Because the excellent engine they are using has no way to make a character swim…true story.
Imagine a rival Dev opening up NW and seeing the walk to the bottom of the lake and no swimmimng. The laughter could be heard @ Amazpn HQ. They wouldnt have omitted swimming if the could in any way put it into the game.
Imagine u got your 50kg voidbent armor in reallife and go swimming. Thats not swimming, thats drowning.
Have you watched Pirates of the Caribbean?
The Undead walk under water.
What happens at the beginning of the New World?
Your ship goes down and you “wake up” in an Island.
That means… everything in New World is actually dead, this is why you respawn after you “die”… It is all an illusion, my friend. We are all dead in the game.
And the water walking is the tip for this mystery.
…
Nah… There is no reason for no swimming. Is really bad to launch the game without.
Vanilla WoW examples;
Portcullis to Undead Stratholme, openable.
Door to Scholomance, openable.
Door to Upper Blackrock Spire, openable.
Burning Crusade; Shadow Labyrinth door, Arcatraz security gate, Karazan had many doors and gates.
Etc.
Lack of time and skill to release the game.
Can you imagine the dumpster fire swimming would be if they added it now? Nothing like a cool swim through Windsward.
Ive seen this before , the attempt at logic. Then the logic fails when someone says ‘When i take off all armour and drop everything I own on the ground why can I still not swim’?
So firing magical fireballs from a staff, zombies, and mystical portals are all believable, but swimming in armour is beyond the realm of imagination?
There’s no swimming because the game is a rushed out untested buggy mess and they didn’t have time to include it would be my best answer to the OP.
Bit fucking mental. What happens if you fall in when you’re like 50m from the shore? 
There was swimming in everquest from day one.
Is this because the water is denser?
You also had to skill it up by swimming afk into a wall for an hour or two 
Even in d&d plate don’t make you less agile seeing it only limits the bonus to dex. It just does not permit great feats of dexterity, but you are still as capable to act and work as any normal human.