After being misled on the promise of the 2x camera on my iPhone I felt the same thing with portrait mode.
On the iPhone Xs (and previous 2-camera lens setups) portrait mode supposedly is possible because of the second camera whereas on the Xr you can get them with one camera. Google for example does portraits with one camera on their Pixel 2 and 3 for few years already and does actually a quite job with that. The same as with digitally stabilizing video on the original Pixel which turned out to be really good comparing to OIS (Optical Image Stabilization) at that time.
Don't get me wrong, I like portraits, even the fake ones you would get from a mobile device. They look noticeably better than regular pictures we had all this time and I'm glad the whole industry moved into that direction. But forcing buying a two-camera phone for portraits is just pure marketing, the same as forcing to upgrade from an iPhone X to Xs for Smart HDR which essentially is a blown-up saturation software-wise possible on the X as well.
Previously the push to new hardware was with actual improvements in it. Now it's just purposeful limitation accompanied by better selling marketing shots. Just like with the new butterfly keyboard on the Macs (which no one actually asked for) that made the product look better on photos but made its operation worse on a daily basis. People keep dealing with it, which let Apple not to fix the flawed keyboard much for three years already. The same reason of people accepting everything lets Apple charge for features on newer devices that technically could have been on older devices as well.
All that said Apple doesn't feel being a pioneer in technology like when I started using their products twelve years ago. Nowadays formerly known copycats like Xiaomi or some even less known Chinese brands are pushing the envelope by building ideas that market leaders can't deliver. Maybe it's not Apple's fault in particular, but it's just what happens with companies that get big. Just recall the huge Nokia back in the days overrun buy a considerably small at that time company from Cupertino which was so far ahead in everything and so easy to recommend to switch to.