Zardnaar
Legend
I think the amount of modularity the fandom expected was far greater than WotC ever promised, let alone intended. I wager WotC thought that the fact that classes had different levels of complexity and options would scratch that itch.
Want a TSR easy class? Download the Basic Rules and rock a champion, thief, evoker, or life cleric.
Want that 3e feel? Pick feats and multiclass.
Want more 4e feel? Pick a warlock or monk and use options like faster short rests and healing surges.
I think there was some interest originally in doing some alternative rules (advanced tactical, Greyhawk initiative) but there wasn't enough demand to warrant further resources.
Even then I think it's mostly a few people online.
People don't seem to use said options they did offer.