So I stole 2 ships yesterday and find it to be lots of fun.
I learned some important things and thought I'd share.
When you steal a ship, you have to register it which costs about 9.6k. Apparently you can't sell the ships for much more than that, but I haven't tried yet.
If you sit in the pilot seat of the ship, you'll see a message about potentially making it your home ship if you take off. If you do not take off in it and just leave, it does not become one of your ships and will disappear if you leave the planet.
if there are ecliptic mercs nearby, attempt to steal the ship before killing them. Sometimes you can, sometimes you cannot. If you kill the mercs, the ship takes off.
If the ship is sitting there, it may be empty and ripe for the taking. If there's a crew aboard, there may be something you can do (chat with the captain and get something), but most likely you'll piss off your companion if you just "take care" of them.
-Unlock targeting to be able to target engines. Once you take down the engines you can board once you get close enough.
-Use an EM weapon to easily take out engines without risking destroying the ship.
-Register the ship in your Tab/menu screen because it's much cheaper than at spaceports. Sit in the chair, go to the menu, click the ship in the lower left, there will be an option to register there. You might have to sit as your home ship first, I forget.
I'm addicted to capturing ships. Too bad there is a 10 ship limit. There should be a mod to increase that but to add maintenance costs to each ship in your fleet.
ETA: There is a mod, basically a console command, that increases the ship limit. But the game seems likely to badly break when you do that so I'll wait a while. https://www.nexusmods.com/starfield/mods/791
Yeah you can hire NPC pilots and crew in X4 Foundations, you can even ride along on the shipping/mining routes. It's a complicated game but I'd love to see some of the mechanics in a game like Starfield or Elite Dangerous.