I hate vertical progression too, but that's modern MMOs for you. Oh well.
I never quite understood the disdain people have for vertical progression. I'm somewhat baffled by what other progression you consider more appropriate? Even with "lateral" progression, you still end up with min-maxing and a fuckton of incidental and situational gear that you have to grind to get anyway. So instead of trading out one suit, you have a closetful of outfits you might wear once a year. I fail to see why this is a better option?
For me it's like a trading card game, when you design lateral progression well it lets people form new strategies that isn't simply "wear the highest tier of armor". Subconsciously I like seeing numbers go up as much as any other RPG player but when you make it so straightforward it makes it very boring to plan your character's progression (The same complaint I would level at the cross class skills being too restrictive, stat points being overall meaningless because you'd rarely invest in anything but your primary stat etc). That's why there's a token cap (myth in this case) in MMOs that choose to do this, because they'll dripfeed peoples' ability to clear the content since there's only really one direction to go (In hindsight it's kind of funny to see people defend this when a lot of the same people were shitting on the fatigue system in vanilla XIV for basically doing the same thing).
Take for example Pokemon's lateral progression every generation. It's true that a lot of those new Pokemon end up being throwaways in competitive battling, but every generation the introduction of new species, new moves, new types, new abilities etc make people think about how to adjust their strategies to combat all the situations they may run into. Previously unviable combos may suddenly become attractive again when used in synergy with other abilities/options. That sort of complexity isn't achieved when all you do is make a bunch of numbers on the players go up, you're usually just making people repeat the same thing with bigger numbers and people eventually see it for what it is.
On that note, perhaps the problem isn't so much that they're asking us to throw away all our old stuff, but rather the "spend another 8 hours per week doing the same sort of grind you already did, just in a different dungeon, so you can get to the content you actually want to play". Most people would probably just go "why don't I go play a game where i'm actually having fun, immediately". The first grind up maybe it's kind of novel, then you quickly realize you're just doing the same thing patch to patch. You're not throwing in any new elements other than visually, you're just asking people to start over a tedious grind gameplay-wise.
I honestly would love an MMO to try out something similar to XI's gearswap system someday, but in a way that actually makes sense as well as making the game designed to support it from the get-go (like maybe instead of swapping out entire suits of armor you're swapping out magical runes during battle etc, also avoid the huge problem the game had with inventory).
XIV's biggest draw for me right now are the fights themselves. I have a lot of fun challenging the boss fights and mastering them. The RPG side of the game isn't interesting in the least, though.