Books (or anything else) written in TeX do not have to use the cmr fonts. I agree that the cmr fonts aren't very nice, but that's nothing to do with getting lon

Books (or anything else) written in TeX do not have to use the cmr fonts. I agree that the cmr fonts aren't very nice, but that's nothing to do with getting long in the tooth; they were not-very-nice from the day they were first made. (Of course this is a matter of taste; some people may love them.) TeX is still holding up well against anything else you might care to throw at it, at least as far as quality of output goes. For typesetting mathematics, it's well ahead of anything else I know of. Not quite so great in terms of usability by the masses, though.