@merikus I've heard good things re Raindrop, but I just wanted to chime in to let you know your initial instincts were right: you can absolutely use Shortcuts and the share sheet to send information to Obsidian. In fact, since Obsidian is all plain text files and markdown, there's a ton of things that are possible via Shortcuts.
I've written a couple of post about this in the last year (in case it helps):
https://www.laroquephoto.com/blog/tag/obsidian
Have fun :)
@merikus Good :)
And yes, that post uses the same basic building blocks—it's just more elaborate. Here's a screenshot of a simpler shortcut I use to save URLs to a dedicated note. You could add an Ask for Input field to enter a comment when you share, and add this variable to the main Text block (just below the dividing line, for example).
Sorry about my terrible handwriting...!
P.S Get Title and Get URL are part of the Get Details of Safari Web Page block