That is simply not true. You could not write a whole CMS with plugin-api, template system, image manipulation, user roles, auto-installer (and auto updater of plug-ins and entire install), comments system, image galleries, media manager as well as a administration backend (that mind you not only needs to work, but also needs to be designed visually) as well as a high quality default theme.
Where do you guys get off saying such things? It's a completely absurd statement. Of course you can't do that.
You're right. I wasn't really thinking about building my own platform; more thinking about building a CMS that did what I needed it to do. The plugin API would take some work, but a templating system, image manipulation, user roles, auto-installer, comment system, and media manager are all very easy to implement, if not provided to you for free by PHP or an existing library (ImageMagick, for example).
Where do you guys get off saying such things? It's a completely absurd statement. Of course you can't do that.