Ten years later, he has no game, only a rudimentary, tile-based dungeon-crawler engine, and reams of code he's written and re-written (as API sands shifted beneath his feet), and the project seems to be permanently on hiatus now. Thus, Casey inadvertently proved himself wrong, and the conventional wisdom (use an existing engine) correct.
As far as OOP goes, 45 years has shown that it makes developers highly productive, and ultimately, as the saying goes, "real heroes (handmade or otherwise) ship." Casey's company was founded 20 years ago, and he's never shipped a software product.
He complains often about software getting slower, which I agree with. Yet how many mainstays of Windows 95/98 desktop software were written in a significantly OO style using C++ with MFC?