I agree that the internet is now essential to solve most puzzles. I imagine the median age of a Listener solver is over 60, so I understand why this may be disquieting.
The Notes for Setters state that “Preference is given to ideas that can be confirmed using commonly available reference books” and “The vetters wish to reaffirm that the availability of thematic information at a website is not a sufficient justification of accessibility”. However, I believe those guidelines are more honoured in the breach than in the observance now.
I actually am all for it. I sympathise, of course, with solvers without access to the internet, but crosswords need to evolve, and the richness of themes the internet provides at solvers’ fingertips is sufficient compensation in my book, as Blakwhole says.