I suspect part of the issue with AoS boredom is that
GW have launched Faction A, then Faction B primarily. Notice that many other games try to launch with 4 factions because that's what they believe you need to create good hype. Yes, AoS already has some legacy factions, but from a marketing and hype point of view they don't count for anything.
Also, Faction A is (IMO) completely uninspiring, so whilst the models are clearly popular (judging by their frequency in online painting groups), from a gaming point of view it's just "more Space Marines, yawn" - mean hell, the 8 Orders or whatever are a completely unsubtle reskin of various
SM Chapters anyway.