I believe that the languages and packages used by kids in school do a lot of the heavy lifting for them. Whereas the Basic or old C that you'd use for the ZX Spectrum would be very bare bones with you having to do a lot of work for yourself. Plus, I imagine that as code development has moved on a lot since then that a lot of the features you'd expect to have available as a modern developer would be missing. I can't imagine that it'd be too easy to develop a game for.