I was pet hunting today, so went back through some old zones - Shadow Moon Valley x 2, Hellfire, Uldum, Tanaris and some others - and I don't know if it is just nostalgia, but it struck me that the older WoW zones had more "character" than those in Legion - i.e. more atmosphere, more story and more coherence. Maybe I am too caught up taking taxi rides around legion on World Quests[1], but I just don't feel any of the zones are very distinctive or memorable - they merge into a blur of Night elf/Vyrkul/Tauren themed mediocrity[2]. And I'm not comparing them to the best of WoW in the past - even Cataclysm and Draenor, which I think are probably worse expansions, seem to have more characterful zones.
[1]I like World Quests, but think it's nonsense to prohibit flying when we are constantly flying round on taxis; and think they should have had more a hub structure - like dailies in Cata - so that they fit into more of a theme.
[2]Suramar may be the exception.