I agree about conditionals and other kind of programming language constructs not belonging in markup. But the point of markup for content-driven web sites is that its a text format and can be contributed by persons other than web developers (authors, site users, syndicated content providers, etc).

You can see a modern approach for this is at work here: http://sgmljs.net/docs/sgmlweb.html ("isomorphic" rendering to HTML in the browser and server-side using full SGML, no less).

Disclaimer: my project