Yeah I don't know. Don't think they should just keep something just because that's how it's always been. Holding back some of the updates to modernity is probably damaging the popularity of the game at this point. Really nice to just hop into a new GW2 or ESO expansion and everything is scaled / levels don't matter.
Doesn't mean I think they should abandon the concept of bar filling though. They'll need to add either an account wide seasonal track like Destiny 2 (they have a near identical system in Hearthstone) or go with some kind of account wide evergreen end game paragon progression system like ESO Champ points.
If you look at what people always seem to complain about it's alt catch ups. With stories, renown, leveling etc. Just leaving it at 60 and having either the account wide seasonal XP or an account wide Alternate Advancement / Champion Point system makes sense at this point.
People will still need to climb the vertical ilevel ladder as they do in these newer games. So you pop into the new expansion, then you can jump right into dungeons, pvp or questing... whatever floats your boat, and that'll start helping you get your ilevel up.