Well you could buy the iPhone 8 and at least get some of the new features like wireless fast charging, True Tone screen, the A11 chip (for future proofing), better camera. I would not buy a standard iPhone 7 at this point.
OLED display, thinner bezels, I'll give you. It has all other performance features that the XS models have. The camera may as well be a wash since you get the core features of the XS dual cameras. You get the same front cameras on the XS and XR as well. I'm really struggling to see how Apple thinks the XS is $250 more expensive ($350 more expensive for the XS Max) than the XR. Other than the OLED display, there really is not any more expensive tech in the XS vs the XR. Considering all the things Apple put in to the XR, and it is available in the 128GB version, it is a lot of phone for the money. It's still less expensive than the iPhone 7 Plus was 2 years ago in in the 128GB and 256GB versions.