There may have been more than one reason the old armor system was replaced as I seem to recall that it was mentioned by the devs that there was a clipping issue with the old clothing and armor system that they couldn't resolve. I can't remember though if it was mentioned on one of the dev streams a few years ago or if it was mentioned in the forums though, only that there was the clipping issue. I thought that made sense at the time, as I did notice at times issues with some of the clothing options shirts, coats and the armor pieces when some of the items you were wearing wouldn't show up, and other times they did. I'm frankly surprised that old system worked as well as it did, since you were adding layers of clothes, various coats or jackets and then the armor pieces. When they couldn't resolve the clipping issue, and I think they were thinking ahead for the finished product that they wanted a better-looking armor system.
I do miss the old system, but frankly with all of the different combinations of clothing for cold or warm climates plus armor pieces, I'm not sure if the old system was really any better than all of the different specialized armor combinations, we have today. I don't believe either system was perfect, but if they added some kind of loadout system like was mentioned, or some kind of outfit storage that was separate from our main backpack storage that it would be a good quality of life improvement, at least from my perspective. I don't like taking up extra backpack slots with extra armor pieces to be switched out for situational use. If they can also add the ability to add dyes to the armor pieces, I think that would also appease some folks that I see keep asking for.