I read your post, and empathize with the notion of "less is more". The problem arises when you want to extend Void. Instead of providing a good way to do so (using templates and a hook system), you force people to code in a single file without structure that quickly becomes a mess. If you never plan to do anything else with Void than what is provided, that's fine, but in my experience website development just doesn't work like that.
* Adding code highlighting? 3 lines of code to add in index.php
* Adding analytics (unique visitor count)? 3 lines of code to add in index.php
* Adding Disqus comments ? Less than 10 lines to copy/paste.
Is it this you call a mess?
I've used at least 10 CMS before, and what I call a mess is more: having to create a SQL DB, having to login/logout all the time, having to understand how the marvellous "install-a-plugin-to-extend-the-CMS" system works...
I have a math research background: if you can prove something in 2 pages with no extra tool, it's far better than doing the same by invoking a big difficult Theorem.
Moreover, I am not a profesionnal developer. And for me, installing Apache+PHP is enough. I don't want to add more tools, more layers. The list could be endless: Let's use Symfony, Composer, Brew (random name here, I don't know what is Brew)... and at the end I'll have a big big thing...
I really want to keep it simple...
Each new layer is like "minus 10 points" for my project ;)