The economic issue is that DoW/M can get tiers of end-game items for less cost from NPC vendors using the same tomes that can be used to purchase end game crafting materials. This results in a dramatic decrease in demand for crafted items at end-game; while simultaneously increases the expense on the part of a producer/crafter: end-game for crafting is not a free market (as a part of a 'working economy') because of the impact of end game NPC vendors and items. Think of it economically as Crony Capitalism with the SE regime deciding the NPC vendors are suddenly going to be the economic winners and player-crafters will be the losers by inflating end game crafting materials in price arbitrarily while killing demand. Or another way economically: the opportunity cost of purchasing AND producing crafted items at end game is too high to do otherwise for most rational purchasers or producers.
DoW/M having access to purchase end game crafting materials at arbitrarily inflated prices (set by SE) is just an extension of the artificially inflated end game economy that pushes out crafters in the first place. And it does more to make the niche BiS items where there is some demand from crafters cost more for DoW/M to actually purchase than need be in a truly functional free market tied into a larger working economy.
Although there are crafted items that are BiS at end-game - for the most part, the economic "end-game" for crafters is going back to making mid-level items for sale on the market while there is still a large number of players leveling up, or offering melding services for tips... it's kind of pointless to level DoH past level 45 if you want to craft items and sale them for profit within an actual working economy.
[And yes, I know there are exceptions in both items and crafters making gil at end game - just pointing out the economic issue/problem at play that leading to the end game complaints.]