I wonder how "classic" they actually mean. Like will it be an honest to goodness reimplementation of vanilla/BC Azeroth, or will be a recreation with an extra layer of spit and polish? I mean, I used to do a lot of out of bounds exploration in my downtime. Areas like Ironforge Airport, the crypts behind Karahzan, the hill regions below the Wetlands, the ones surrounding the Forsaken starting zone, etc, etc. For me at least, being able to find these sorts of "backstage" areas and working out ways to get into them was a big source of "chill time" fun (that and fishing). It'd be a shame if those areas end up properly closed off, or deleted entirely because Blizzard decides to put stricter security in the fun park.
If I understood Blizzard correctly it is going to be a faithful reimplementation, so e.g. Paladins just being garbage, maybe the updated character models, but no dungeon finder, flying around, and all the good, old annoying stuff people have been asking around for ages to experience again.