... because dropbox is cross-platform, user-friendly, doesn't require use of the commandline or configuring an upstream source, has a web interface, simple sharing with others, etc etc etc etc

Those kinds of "can't you just..." or "why use [easy user-friendly popular thing] when you could [complicated nerdy feature-bare alternative]" answers are rarely helpful and typically come across as condescending.

Yes, there are complicated containerized or fancy disk volume spoofing workarounds, and there are also alternatives (I like SpiderOak), but none are as simple as using dropbox was.