It doesn't add anything to the game.
It does not make gearing more interesting, and it forces odd breakpoints.
You either have too much or too little, and especially as there is nothing that tells you how much you "should" have, it is a stat that is confusing to newcomers, and frustrating to plan around for others.
Do you really need a different set of gear for each raid? Apparently you do if you have accuracy as a stat.
At the beginning of gearing you will have far too little, leading to frustration and misses and breakdown of rotation. At the end, you will have far too much, and there is very little more frustrating than watching an "upgrade" drop that literally has a useless stat on it. All stats, whether preferred for your build or not, should be at least somewhat useful, instead of being the most important when you have too little, and utterly worthless if you have too much.
The problem of accuracy is its all or nothing aspect of it.
It unduely penalizes entry level gear, and ends up being useless or bloated for those in endgame gear. It is the only stat in the game where you must get "enough of" but never "too much" of.
It is also the only stat in the game that can seriously change your rotation - a miss is very painful. It is funny to me because those that argue for its existence really argue for it to not exist - because as long as it exists your primary job is to make sure it doesn't...that you always land every attack. That is...hilarious.
As for the gearing ramifications, I guess I am not following your complaints. Without accuracy you have more gearing choices, not less. Instead of going "ugh, I can't take that piece, I'll drop under accuracy" you'll go "hmm, I wonder if the increase to crit is worth the loss in det" etc, moreso than currently. I fail to see how this makes the game simpler or less interesting, if really staring at numbers is your thing rather than going out and killing stuff. And in that spirit of "lets go out, get phat loots and work together to kill a dragon", the last thing I want to see is my wonderful attack missing, or the middle attack in a combo missing and screwing up all my timings (monk and dragoon especially).
Lastly I want to address the whole "accuracy v. evasion" thing. There can be one without the other. If the goal is to allow people to dodge - let them dodge, this is a game mechanic and a cooldown that makes sense. If everyone has baseline 100% chance to hit - you can still have Featherfoot give you 20% chance to dodge or whatever - its clear to player what is happening, and it allows you to tweak passives and actives without being bogged down by scaling numbers. I am all for more player knowledge - this obfuscation of what accuracy is, how much you need, etc. just ends up being another vague SE stat which we don't really understand.
If you want autoattacks to miss 10% of the time, okay! If you want a certain skill to always have a lower hit chance (like thunder in pokemon), okay! Do it with percents and very obvious information, not a "get and forget" stat.