I too moved away from 3.x to a simpler system - I prefer C&C, but the truth is there is a stong movement out there that is discovering that the mass of 3.x and d20 products has just become... well, cumbersome is a nice word. You have to experience a game or a session once without 50% of the time being devoted to checking references, rules for every single action, etc. before you realize just how much fun it can be to go an hour sometimes without rolling a die. I do not decry devotees to 3.0 or 3.5, and I do think some carry their distaste to extremes... if you like it and have fun, play it.... I played 3.0 for several years - and I still use the core books and early supplements to port house rules and ideas. But I find it always easier to take simpler rules and add on than take massive rules and attempt to pare down - especially when its just human nature for players to say "but it says here on page...."
The biggest difference between older systems (O/AD&D), newer brands (C&C) that seek a "rules lite" approach and the 3.x/d20 systems always comes back to one essential difference - 3.x and d20 are mostly concerned with WHAT a character can do (heavy empowering of PCs) while the older and alternative systems place the emphasis on WHO the characters are. If you prefer your characters to be fantasy superheroes, then I say no problem - go forth and game (3.x and d20 has you well covered for good material for this style)
There are a lot however that have experienced "rules" burn out, and so it's never surprising to see someone else say "oh my, I never knew how much fun this older system could be." To them I also say just have fun and don't let anyone tell you "that's insane."
The only problems occur when people want to start throwing words like "true," "perfect," "good vs. bad," and seek to somehow convince everyone else that their way of playing is the "right" way and everything else should end. The saddest part is when people try to drag in writers and creators, be they "legends" of RPGing or current well-known names, and create "edition wars" that somehow seek validation for them as individuals.
Everyone of us is an individual with our own likes and dislikes.... and there's gaming material out there for all of us.
