The problem isn't that C++ templates are Turing complete. In fact, many similar macro systems are. The problem is that the result of template/macro expansion may affect the parsing of other places, so you can't parse the non-template parts separately from the Turing-complete parts.

I don't feel as though the article is making value judgements based on the conclusions. At least I didn’t see anything. The implicit conclusion may be “wow, C++ is ridiculous,” but to be honest I didn’t feel that kind of tone when reading this article.

That doesn’t mean it doesn’t matter though. The decidability of C++ grammar certainly matters to folks that are parsing C++ code.

I don’t think it was designed to be Turing-complete, so it’s a lot more annoying than it could be when you try to use it this way.

The early template designers specified a limit of template recursion (16 IIRC) which they thought was more than deep enough for any real use, and would ensure that it wasn't Turing complete (truing complete of course requires no limit to template recursion depth). However soon after people started finding deeper template recursion depths were required for the real problems they wanted to solve.