I did use the gi the first few months, and then the school made it optional and almost no one wore it. Within a few months, the guys that had been taking classes a year or two longer than I did complained that they couldn't do anything to me without me wearing the gi.
The argument has been done a 1000 times, and the proof has is now seen many thousands of times over in the cage events. The "importance of the gi for technical purposes" is only valid if the other guy is wearing a gi. What good is the technical purpose of practicing grabbing and manipulating sleeves, cuffs, collars, etc., that aren't there?
The gi is an anachronism. If you like a martial art that is anachronistic, fine, but don't require others to go through the futility of wearing and learning and paying for that anachronism when they don't want it, don't need it, and for MMA is a disadvantage.