Yeah, but thats one dress locked behind that (okay, to be fair: a bit more than only one dress, but thats not changing the point I want to make now).
There are other dresses in the game - some a lot easier to obtain (MGP, vendor in Ul'dah, cheap, undyeable versions of more expensive gear), some just slightly less grindy (stuff that requires mats from old maps - it drops more frequently now - or mats from diadem). Some quests are just handing out gear aswell, events are prominent for that too. And over time the're making the mats for the new stuff a lot more accessiable aswell - when the new stuff isnt the new stuff anymore. Just look at what happend to some of the rare drops from Aquapolis, like the wool top: they got added to the yellow scrips vendor. They were special for a while and offered people who didnt craft but got lucky a way to earn some gil aswell - and now they're "easy" to get.
Same goes for mounts and minions - there are those that are easy to obtain and then those that are locked behind a grind. Everyone can have a mount or minion - maybe not a very specific one, but its not that you cant have a little pet running behind you all the time.
- at this point I'll stop replying to the quote and just speaking in general again -
They've created all those "systems" (I'll call them systems because I need the word content for another thing here) in the game: Dungeons, Raids, Primals, Crafting, Gathering and Fishing, Gardening, POTD, Treasure Maps, Airships/Submarines, FATEs, Quest, Achievements... and all of them need rewards to make them worthwhile. Needing rewards isnt a problem here - before someone comes in and says "They should just create content thats fun enough so you'll do it without a reward", its a very human thing to look for the carrot.
Rewards for dungeons, raids and primals is esay - their primary rewards are gear. The devs can safely assume that a waste majority of the playerbase is going to do at least the dungeons, so they'll get tomestone gear. Since most people will be doing dungeons, gear thats needed for progression can be a reward - it locks basically no one out of further content.
Not so much with the other things I've mentioned - not everyone enjoys crafting, gathering, fishing... not everyone runs treasure maps and not everyone has access to a garden or an airship. But (some) people still leveled their crafters and geared them up and want something to do for/with them now. Some people got their fisher to level 70 and can ask "Okay, and what now?". People are getting treasure maps and need a reason to bother opening them. FCs are putting the effort in to build vessels - what for? I'm standing infront of my garden and asking myself "What is worth planting?" - and that cant be something thats needed for real progression, so it has to be cosmetical.
There are cheap, but still good looking options for glamour/mounts/minions in the game - if you want something very specific though it might be locked behind something that looks like an aweful grind to you, because it comes from content you werent intrested in until now - and that you're still not intrested in, but now you want that reward. Go and earn it (or pay someone for it).
Lets look at the Moai Minion the OP mentioned again. And look at it from my perspective:
1) Have BSM at level 70 - check, done months ago
2) Have the gear for BSM - check, done months ago
3) Get the mastercrafter book VI for BSM - eh, an hour max of red scrips
4) Get the Royal Fern - check, done that weeks ago because I predicted it would be the new blood pepper
5) Get the Colossus Slab - okay, submarines are my guess, not sure yet.
If you look at it from the perspective from someone who wasnt intrested in crafting and gardening til now and is only intrested because they want this minion, that probably looks awful because its a lot of effort for a minion.
If you look at it from the perspective from someone like me, who spend their preparing for crafting endgame-crafting-gear, its a nice little extra thing I'll be able to make. A nice little extra reward for all the effort I already put into it. Something less boring than the 100 frying pan the BSM can make.
Keep also in mind that you can juyt buy it - eventually.
You're looking at this like a level 15 character who just did Sastasha looks at the current Savage-mount and goes "I want this now!" and then gets told what they have to do to reach that.