Not suprising to hear three things:
1. The best programming language is the one you are probably using at the moment, although it assumes you would pick the right langauge for the job at hand.
2. Mixed language projects are problematic.
3. The ability to migrate ownership of a codebase and bring new engineers up to speed is very important.
I think we all recognize these things as self evident but, I certainly, have not always had the discipline to keep front and centre.
Remember, "A little bit beyond Hello World" in Carmack's mind is Video Decompression code. Brings a little bit of perspective.