I can happily say your right but also just a little wrong in the best possible way. These guys https://www.numworks.com are building a “modern” graphing calculator, using an ARM Cortex-M chip and ABS plastic... but it’s an open hardware and software design that is documented and tinkering friendly.

I haven’t needed to buy one yet since the second hand CFX-9850GB PLUS i own is still working well enough for me, having picked it up out of nostalgia for having used that model through high school and university, but if that ever breaks I’ll buy one, I may even buy it before hand just to support their excellent work and commitment to open hardware.