The thing I most appreciate about Obsidian is, for now at least, they at least partially embrace a sort of FOSS mindset in that they offer a proprietary thing via a sort of compromise: your data is stored in plain text in markdown, so it remains 100% portable and parseable by anything which can parse markdown.
But I get what you mean.
Via their Sync service, yes. If you’re in the Apple ecosystem, they officially endorse iCloud to sync your files, which I personally use. They discourage using Dropbox, but I reckon it’s possible.