Yeah, I've had a mixed experience with playing with some randoms. Some are really good, some are dogshit. I mostly play with people I hang out with all the time, and we're usually in a group of 4 so for us it's been excellent. And when we've had to bring in a random, it's been 50-50 if we're going to get someone who communicates or if we're going to get someone useless (that we then vote to the brig and tell to fuck off lol).
I agree, I was disappointed to learn that stealing a ship was something we couldn't really do. I also feel like the absence of merchants/fishing vessels means we can't do some vintage piracy on the high seas - when you see a ship, you'll know it's another pirate ship. NPC ships would have been very cool.
But I do steal loot from ships all the time, the method my friends and I do is keeping 2 people on the ship to fire cannons and keep the other pirates from hopping on board, then 2 people going on board the other ship, one to grab chests and one to drop the anchor and generally fuck with the other team. If anyone dies off the ship, when they respawn they'll rotate to the ship duties and someone on the ship will jump onto the ship (usually with a powder keg if we've got one) and try to swap a chest for a powder keg and sink the ship. By the time it goes down, you should have lifted a few of their chests. And if they've got a lot of them, they'll be in the water after it's sunk too - so if you kill them off quickly and have them sunk, you've got a bit before they'll come back for you.
Last night we went on one of those raids, with 2 other pirate crews. And while the raid was short, the aftermath of us grabbing the key and high tailing it the fuck out of there to come back to get the loot later took us 4 fucking hours. 2 ships chasing after us, countless naval battles, lying over the voice chat to strangers that we don't have they key, and some good use of having someone hide on an island with a key at the very end... made for a pretty fun night last night.