I'm probably using style sets in a different way.
I use them to manage the styles gallery. I make a style set for each template I create. It has all built-in and user-defined styles that may need to be applied later. This is the one that I and other formatters use. Another style set based on the same
template is for for writers. It has fewer styles (say, normal/body text, list bullets 1 and 2, headings 1 to 5, caption, table heading, table text, and table bullet)--just enough to help them show the document's structure. I find that writers use styles
more often when they are easy to find—right there in the styles gallery at the top of the window. I still use the styles pane more often, mainly because I have it set to display all the styles in the document alphabetically.
I use them to manage styles gallery clutter. In some versions, every time a style is added to a document, either deliberately or through pasting, it automatically gets added to the styles gallery at recommend level 1. These unwanted entries push wanted
styles off the first line of the gallery. I get rid of them by reapplying the style set. In W2010, I could click the style set name to reapply it or I could choose to
reset quick styles (read style set) from template or reset document style set. W2016 only offers
reset to default style set--I haven't taken the time yet to figure out what that means (normal.dotm, the document template, the document itself??).
I use them to manage multi-input documents. When I get documents piecemeal and they must for a time remain that way, I can get the styles I need to format them very quickly by applying the template's style set. The big up side of this is that the template's
default settings get transferred too (which doesn't happen when you use import/export (aka the organizer)). The downside is that table and list styles do not get transferred (which import/export will allow you to do).
I also use a style set to get rid of the clutter that comes in normal.dotm. I created a style set that omits the stuff I don't want in the styles gallery (book title, intense emphasis, etc.) and puts in the stuff I do (list bullet 1, caption and such).
I get rid of them in the styles pane too.
In W2010, the style sets are listed in a nice neat little drop-down. My style sets show at the top because I started each style set's file name with #. So there they are, immediately clear and available. In W2016, I have to hover each badge for 2 or 3
seconds to see the style set (file) name. This is slow, and I'm more likely to make a mistake.
So, yes I do agree that this change is for the worse. I don't know that I would have come to understand the relation between style sets and the styles gallery with them as far apart as they are in W2013 & 16. I suspect the people who split them up don't
get it yet.