This is similar to my experience. To this day the decision to make wotlk heroics aoe-runs without aggro issues, etc., from day one (I mean pre-3.1) was, in my opinion, bad business in terms of pretty much destroying content longevity. All that work they did for 12? new instances, and they became, for the most part, laughable content almost immediately.
To most players even able to do heroics in BC (esp. with revered keys), they remained on-your-toes content until very late or the end (though kara badge introduction really reduced participation in them), though I realize now with it being 5 years gone, everyone (TBC HEROES that now appear on tbc threads) was in t6 and everyone ran h mgt with their eyes closed pulling the entire instance and everyone cleared all 15/16 lockouts daily, etc.
- - - Updated - - -
Also blizzard has engaged in a fair amount of player-base selection/deselection - anyone that attached to the older game-states/tuning/design philosophy etc vs. more recent versions has, at this point, simply left.