as a mate once said to me "people ain't getting dumber, we just get less tolerant of stupidity as we grow old!"
and i dont really see that codices are getting simplar. i recently had a chance to see some of the old 2nd ed books again and i couldn't believe how basic they were! very few unit options to speak of and all character wargear was on seperate cards that listed their rules and points on them, so you didn't even have to remember what stuff did!!! so all you had to do was find the cards you wanted and keep them to hand
by comparison 3rd and 4th were a bit more complex, as you had to flip through the dex to add up the points for a single hero, and 5th is the most complicated yet as all the rules for wargear are spread through out the book rather than being listed on a few easily found pages. sure the stuff is easier to pay for but finding out what it all does mid game involves much more page flipping!