New players could be exposed to it slowly over time, just like most aspects of the game. You don't need to add weapon effects, horizontal progression, or gear sets to any of the 1-50 content. Even with that point in mind, GC vendor gear already exposes leveling players to set bonuses and item effects. So to that part of the questions, I would say it does not seem like a valid concern since new players are already being exposed to such concepts on live servers and the meat of the system would be waiting for them in the end game.
There sould be less focus on "what about the new players" and more emphasis on what currently subbed players want. This game has over 5 million accounts but can't keep a fifth of that as active subscriptions. Horizontal progression is something people have been asking for since 2.0. Maybe the cookie cutter content with vanilla stats needs to be reconsider? It seems troubling to me that this game has blow through over 5 million players and has only retained less than 800k active subscribers (which is probably being generous at this point).
Added horizontal progression can give players more to work towards. It can give rewards more staying power when the items attributes and worth are not just defined by ilvl. Adding depth to the game engages players more on a cognitive level and can help with player retention.
I was not rude or brash in your bolded segment. If people are rude or harass other players, we have GMs to take care of that. Your concerns of rude scrutiny are already covered by a code of conduct included in the ToS. Otherwise, if a player wants to play their own way, they should play with like minded people and this game is FULL of laid back casuals that don't care about a person's optimization.
Yes, The whole concept is to bring choices, but I was addressing a specific concern about an item being generally accepted as better for a certain fight. You can have both choices and and items generally considered better for a fight. A good example of this paradigm in work is blm on a6s. You can either use a max ether and get an extra flare off on the five dolls or use a max pot of int. Both are good dps gains for a blm, both choices suffice for the fight. A BLM choosing option A or option B will not prevent the group from getting a kill. Is one choice better than the other? Sure. I don't have numbers in front of me, but I would try the max ether 1st and see what dps gains I get from that. Results aside, this is a novel personal choice that adds some depth to this situation. Before max ethers, this situation would have never been possible. I don't think it's unreasonable to ask that this same paradigm be translated to gear. As it stands now, we don't even really have gear builds, we just have "maximize your preferred secondary and hit acc cap, donezo!"