Ah, I'm with you now. And yeah, I do agree that a line has to be drawn somewhere. exa would probably fail if used with a screen reader, or heck, it doesn't even work properly under Windows right now. That's a huge market I'm ignoring!
What I've seen people doing is saying that there's no line at all: every feature needs to have its cost justified, every type of user scrutinised to make sure they're not dragging the product down. This is expected behaivour for startups (launch to a limited market first) and big companies (where you need to justify every cost) so I'm not surprised to have encountered it here.
For colourblindness in particular, though, I still think there has to be a way for the default colour scheme to be colourblind-friendly without the experience for everyone else suffering as a result.