I disagree; file syncing is still exactly what I want. Disk space has gotten exponentially cheaper over the years, and at the same time the amount of bulk media that people store as personal files has been dramatically cut down thanks to streaming services for music and video. I don't mind at all having my entire Dropbox mirrored across my devices; it holds basically every local file I care about, and having a local copy also gives me some peace of mind in case I ever get locked out of my account or something (which Google in particular has become notorious for). You can also, now, select subdirectories that you want to exclude from the current device. At the same time, having it in the cloud means I don't have to worry if my hard drive dies. Any file that I've thoughtlessly kept there while working on it is safe by default.
Maybe the story would be different if I ever created classical "documents" and could benefit from Office 365 or Google Docs, but I don't, and so having a cloud-first storage "drive" that primarily holds things which integrate with that particular cloud service isn't very useful to me.
> But their growth chasing leads to a degraded user experience
You're right that parts of the product have gotten distracted/annoying by trying to build out new differentiators. But the core product (file syncing and backup) still works much better than competitors, and it's not hard to simply ignore the new stuff.
Also, perhaps most importantly: I use products from multiple tech giants, and all three major operating systems, and I specifically don't want my cloud storage to only integrate well with one of them. I want it to work equally well across everything. And Dropbox does, at least compared with the competition.