That's only part of it. There's also the phosphor masks, etc. It's not that we literally don't know how to make CRTs any more. But the manufacturing ecosystem

That's only part of it. There's also the phosphor masks, etc. It's not that we literally don't know how to make CRTs any more. But the manufacturing ecosystem is gone: the machines, the tooling, etc. That was the product of 80 years and many billions of dollars of R&D. Making high-quality CRTs requires some pretty specialized propietary gear. We could probably manufacture a 1950s-style black and white TV without too much effort. But it would be a tremendous leap from there to creating e.g. a high-end Triniton monitor capable of doing 1080p@120hz.