If you think the way humans can control units better is a "feature"
You hit on the exact reason yourself:
submarines (they can one shoot most ships)
Imagine the situation: you have your naval armada with a destroyer deployed several tiles away from the main force in every direction to screen for subs (or subs of your own, doesn't matter) and a main force of battleships and carriers.
You're moving across the ocean, trying to make sure you don't lose a precious carrier full of planes or valuable promoted battleships to shell cities.
Then suddenly all your battleships and carriers are dead because the AI moved in its submarines and sank all of them in one turn. Because nuclear submarines (which have a base movement of 6, 7 with either Great Lighthouse or Exploration, 8 with both -- not even including England) literally moved six spaces and fired a further three in one turn to one shot your ships. That's 9 spaces covered (and if they have 8 movement from both bonuses and the range promotion that could be 11) in one turn, effectively.
That's basically nigh impossible to defend against even with your own destroyers/missile cruisers/submarines specifically deployed to stop such an attack. And given the swarms of units the Deity AI gets, the problem becomes even worse.
Or take another example: you have a city on a coast which expands 3 tiles into the sea. That means you can see 4 tiles out. You decide to plant a nuclear submarine 3 tiles out from your city which gives you an effective vision range of 6.
Then, one turn your city has a fleet of battleships/missile cruisers swoop in from 7+ tiles away, bombard the city to 0 HP, and capture it with a destroyer before you can react.
And you never saw it coming despite the nuclear sub trying to watch for it and the city having a good range of vision.
To summarize:
AI controlled Composite Bowman moving 1 space and firing 2 for a total range of 3: no big deal.
AI controlled Rocket Artillery moving 1 space and firing 3 for a total range of 4: no big deal.
AI controlled ship moving 6+ spaces and firing 3 for a total range of 9+ WHILE also often one-shotting its target unit: big deal.
Naval combat simply is too lethal and has too long of an effective range for a turn based game. It's broken in general, and I think the developers figured it was better to simply not have the AI make the player rage by exploiting it.
It simply wouldn't be fun for the player.
No need to criticize anyones play cause he's used to stealing workers. Most Deity players are doing it.
I'm a Deity player as well -- and what annoys me is the ENCOURAGEMENT to do it. If random player A decides he wants to worker steal like crazy, well, he can do whatever he's comfortable with. But if he insists that random player B needs to "improve his game" by worker stealing, that's something else. See the difference?