I MUCH prefer "he/she" to "they" because for the 80 years I have been on this planet and speaking/hearing/writing English, "they" has been used to indicate plural/more than one person. I find it annoying and a bit confusing to read an article where "they" is used throughout and at times it not clear whether one person or more than one person is being written about. I do respect and understand why someone who is binary or uncertain about how they want to identify themselves does not want to be called "he" or "she" when they don't feel like a "he" or a "she"...... We humans are indeed not precisely cut-and-dried, to be viewed in absolute terms of either-or; there's a lot of continuum in between one "absolute" and the other "absolute." Many human beings (and perhaps animals as well) are more gender fluid than that, and this is fine.
The problem is that we all do need to come to some sort of agreement on what terminology and pronoun preferences can work well for all of us and that would also make written and spoken communication much clearer. For me, "they" does not cut the mustard. However, of course if I meet someone in person or am communicating in writing and the preference is for "they," I certainly do respect their choice and go with it.