You're not wrong, but there are a couple of things here that rub the me wrong way.
> Of course, but most consumers outside of tech enthusiasts have no idea which stuff in their laptop is upgradable, even when it is, so they just buy a new device whenever they want to upgrade, because that's how they've been conditioned by the industry.
While that's true, that doesn't mean it should be that way. Having everyone buy a new device whenever they need to upgrade makes business sense for device vendors but IMO we definitely shouldn't encourage regularly tossing out good hardware. Not with the ecological costs of new electronics.
We don't need to turn everyone into a tech enthusiast or a computer service person. But if part replacements and upgrades were possible and people knew about it, a local shop or someone else could do the job for them.
> Come to think of it, even upgrading the multimedia unit is a hassle in modern cars as each unit is locked to its production vehicle.
The original comparison to cars might have been unfortunate (as usual), and you may be right that things aren't that different with cars. But again, things being in a certain way with cars doesn't mean that's how they should be with other devices. Or with cars, necessarily, but I don't know much about those so I'm not going to argue about that.