The glued-in battery makes fixing it at home harder, but comes with significant weight and space savings. It’s a trade off, like so many things and many people (including me) are willing to accept it. Apple is not the only manufacturer to do this, my Thinkpad has a non-user-serviceable battery as well. It’s not like the battery cannot be replaced, and I’m willing to have my machine serviced at an authorized repair shop when the battery needs changing. In exchange I get a lighter and slimmer laptop that I lug around every day. The cost for a battery change on a MacBook is just slightly higher than the battery for the older models.
This may not be a trade off you’re willing to make, but it does not make the machine disposable.
My Thinkpad Carbon X1 has a user-replaceable battery and is practically the same weight and size as a MacBook Air. So it is certainly not a compromise I agree with.
The "disposable" label was a bit harsh, but there are other compromises in the MacBook Pro, for example the SSD, which is more prone to failure than other components, is soldered on to the logic board.
We may have a different notion of "user-replaceable". I'd only consider a battery that can be swapped without opening up the laptop user-replaceable.
Soldering the components to the board is the same kind of trade-off: It saves weight, space and increases battery lifetime. You also compare the relatively new X1 with an outdated (though still sold) Macbook that was designed and built at a time when no laptop even got close to the size, weight and battery life of a MacBook Air, especially the 11" version. There were other laptops just as small, but they'd compromise on battery life, others that had the same battery life, but weighted more.
Granted, it's certainly an extreme compromise, but I know more than a handful of people that would never trade their 11" Air for anything else.
You can, btw., have the SSD changed, it's not soldered to the board for Airs. It's just an uncommon form factor that few vendors sell. See https://everymac.com/systems/apple/macbook-air/macbook-air-f... for example
This may not be a trade off you’re willing to make, but it does not make the machine disposable.