This is true, because when brought up, a lot of people want to associate Geomancers with "spell is based on terrain/weather" which is where the idea that they couldn't work well in an MMO setting might stem from. However, if XIV's Summoner, Scholar, Bard, Astrologian and I suspect possibly Red mage are anything to go by, what you best remember the job for can be changed/omitted to suit the game balance's immediate needs, with only aesthetic details barely upholding its "identity." Who's to say a XIV Geomancer wouldn't get weather and/or terrain flair in their abilities; only for it to mean nothing as far as element/resistances go?
Oh, of course it wouldn't. A lot of XI's job gimmicks would never work in this game. Inspiration loosely meaning for light example, a totem/turret/whatever is dropped via Sacred Soil, Flaming Arrow, Asylum, etc. that has a different effect pending the direction the player was facing upon activation. Or even inspiration in the fact that it as a job went against the "terrain = attack affinity" grain and did other things with it.XI's GEO was basically a walking buff/debuff totem with a horribly contrived "face a different direction for varying effects" gimmick. XI's combat was slow enough that you could sort of get away with how GEO was implemented (nevermind that it became mandatory because of the nature of its buffs, which is something we want to avoid here), but that wouldn't fly in this game.
Well Geomancer wasn't only about traps in Explorers. It could create either a buffing or debuffing AoE zone where certain abilities gained different boosts if used within the corresponding zone. IMO its a start to build a job around if there needs to to be decisions about which floor field to set down, not unlike BRDs choosing which song to have up, which fairy a SCH uses, etc. I'm not saying it has to be totem/turret/field job, but the connection/framework is there from past iterations. No actual terrain necessary.The only thing that I can see working from Explorers would be something based on Traps, but that would lose a lot of use in raid fights. It's also not enough to build a job around.