They actually have a legit reason for not doing a free trade server and have historical precedent besides the non-answer about breaking the 'core gameplay loop'.
It would be a CSR nightmare and they are already understaffed on purpose because most companies are leaning towards automatic solutions for most CSR issues (character deletions, item loss, item sold to a vendor, etc) - not to mention that they had a high amount of people using stolen credit cards and chargebacks back in the day that lead to a lot of innocent players getting banned. I've seen that with a game that I did CSR'ing on professionally; they'd have a lootbox that had a tradeable item in it, people would use stolen CC's or Steam accounts to get the item they'd gamble for, followed by chargebacks and banning of the daisy chain of players that got tangled up in the illegitimate transaction and ultimately ended up with the item.
Now imagine having that, plus the larger-scale RMT problem EQ has with Redguides/ECTunnel/PlayerAuctions/EpicNPC - you'd ban so many players, lose out on money, and have to staff up your CSR department for one server that might last a grand total of 3 months. Yeah, I can see why they aren't doing it.