Some rare Affix (such as Stone hide and Incorruptible) are very powerful, but most are garbage and not used much.
Also, unless you use external tools, it is much more difficult to find any Affix than to find a legendary, but lacks the appeal of surpassing the legendary.
Re-tuning Affix is a very difficult task, but treasure that is strong but attractive but difficult to obtain is a good incentive for treasure hunt. Originally, the legendary should be in this position, but since they are too readily available, I think that more attractive Affix should be added.
That aside, to the OP…I agree we have far too many affixes IMO. But, that said…If we had less, the good ones would be less rare, and thus less valuable.
Supposedly in the expansion, Resist Capping will be easier…I don’t know if that’s true or not, but if it is, that will drastically change how rares are viewed and which are sought after.