How is someone who has an entire lifetime of experience brewing english beer meant to brew very good beer in another style, one that they don't necessarily have a palate for, or any genuine interest in?

That's a recipe for disaster.

Also, there has been a movement toward more sessiony beers in general in the last few years in american cask beers. You can fill that in any number of ways, but there's nout wrong with using English beers to do it if that's your expertise.