And we all claim that softwares always have bugs, and must evolve. Sometimes I think we are just justifying our own lack of dedication and hard work for a perfect design that is stable and does the whole job correctly since beginning.
To give one example where TeX hasn't evolved, and which I think is a wrong decision rather than "perfect design": its Unicode handling is atrocious. Of course, this is because Unicode didn't exist when TeX was designed. But now it does. In fact it not only exists, but is the default text encoding on most contemporary machines. My locale is set to en_US.UTF-8, for example, and I'd therefore expect my toolchain, from grep through TeX, to be able to handle UTF-8 text. But TeX chokes on it.
(Fortunately, the developers of pdfTeX aren't as averse to adding new features as Knuth is, so I've switched to that.)
To give one example where TeX hasn't evolved, and which I think is a wrong decision rather than "perfect design": its Unicode handling is atrocious. Of course, this is because Unicode didn't exist when TeX was designed. But now it does. In fact it not only exists, but is the default text encoding on most contemporary machines. My locale is set to en_US.UTF-8, for example, and I'd therefore expect my toolchain, from grep through TeX, to be able to handle UTF-8 text. But TeX chokes on it.
(Fortunately, the developers of pdfTeX aren't as averse to adding new features as Knuth is, so I've switched to that.)