I’m in the same camp as @Shamino. I used to use it because I liked being able to indicate important stuff by giving it a background color in my usual column view layout. But when they switched to tags that background color became a little LED next to the item. That essentially broke what I was trying to do. So I stopped using it. In Mail it still works the old way and there I still use it too. Of course there I miss that it obviously doesn’t sync over IMAP so its usefulness cannot extend beyond one Mac.
I originally thought them a fantastic idea, but I’ve found the tags don’t always “stick,” which makes them of limited utility.
I don’t remember if I had issues with Dropbox client, but once I switched to Maestral, I noticed that it doesn’t honor tags when it syncs files, so say, marking a file on one computer with a “red-important” tag doesn’t get that marked on another computer, which is confusing.
(Same with tags to indicate I’m done processing a file. When I go another computer, I can’t tell which files I’ve edited and which are still to-do, so I end up putting things in folders to indicate status instead.)
I still use tags, but just for casual, non-essential reasons, like marking which videos I’ve watched or want to watch on my media server (which aren’t files that sync). If it’s anything crucial, I add text to the file name or use a folder to do what I should do with a tag.