See that is what I disagree with. Your post is nothing but a generalization. Right now crafters either specialise in markets or do a little bit of everything. The first group is the one giving you trouble. And as you mentioned being a specialist yourself, that group includes you.
The difference between the other specialists and you is not ''level of specialization'', it simply the amount of time they put into it.
You cant compete with them because they simply have more time to spend.
Not because they ''have 4 retainers with goods from every market''
Do you know why people will have certain goods stocked up in extremely large numbers?
Because they specialise in that market.
I don't believe there is a single person that has ''every 4 star equipment posted on the mb'' either.
[Example]
I am doing that right now with nuggets. Not because I'm some nefarious trade baron that controls the servers board.
But because I happened to accumulate about a dozen stacks of gold ore (partially due to TT time windows).
This effectively makes rose gold nugget a market I specialise in.
However, since I can make gil in any number of markets, I won't always even have nuggets on the board.
This would change if the system forced me to specialise, and gold nuggets was something I would take to specialise in.
Since I'm now unable to change markets at will, I have no choice but to focus on this market.
Result: I become a permanent presence on the market, one capable of farming a good deal of materials on daily basis.
I would likely produce 2 more alts, trippling my production.
-> casual crafter/gatherers that also chose this as their specialization would fail to make gil, because I would always be there to undercut them.
--> another hardcore crafter produces similar amounts as I do, with the same time available for undercutting.
Result: the market crashes, the item devalues greatly.
[/Example]