This is true for every note-taking app with an export functionality. And it really isn't good enough.
The entire reason you use Obsidian or Notion or Anytype or Capacities.io or Logseq, or anything more powerful than a set of markdown files in the first place, is that you care about the relationships between the notes and the rich functionality that comes with them - sorting, search, linking, reminders, etc. None of this is easily exportable into another app. The series of markdown files that make up Obsidian is not a substitute for the Obsidian software, nor are the relationships easily rebuilt in another app.
The difference between all the other Apps you mentioned and Obsidian is that in Obsidian, it it just a layer on top of your text files (Markdown) and do not ingest in its format.
For instance, with Notion, I have to be able to export that and figure out how I fit in to the next Awesome Note App.
What I like about Obsidian is -- I don't have to. The day I want to walk out, I just walk out and use the next tool that can look at my content and do its magic.
The caveat is, I make it my discipline not to use tool-specific features. For instance, Obsidian has a really nice Plugin called "Dataview", I use it at times but don't depend on it. I can walk out and nothing gets lost.
Own the content, then use whatever tool you like on top of your content.
If all you're using Obsidian as is a fancy markdown editor then of course you lose nothing. But the whole point of PKM apps is that they're more than a fancy markdown editor.
Without the tool, a Kanban board that remains as a bunch of scattered markdown files is worthless for its intended purpose, and not easily recreated in another app.
It's like, a Microsoft Word document is perfectly portable if you never use any of its formatting features and always save it as plaintext, but at that point is it really using Microsoft Word?
Obsidian vaults can be converted into formats that work with competing PKM tools. I swapped back and forth between Obsidian and an open source tool based on Visual Studio Code for a while.
If you use a subset of its features and don't rely on any particular plugins, yes, you can seamlessly convert between some tools — because in the end, it's just Markdown and some basic features like tagging and linking are shared.
"But my workflow is portable!" is really not a good response, when a workflow like OP's, or even one that depends on a few key plugins, becomes very much not portable. The more you buy into the ecosystem, the less portable your workflow will be. "Don't buy into the ecosystem" is not a reasonable take at all because that's the entire point of Obsidian over competition, the (mostly open-source) ecosystem that they have with the first-mover advantage.
What will you do if they stop developing? Start maintaining the code yourself? Wait for others? Very few open source projects thrived after original author lost interest.
You’re moving the goalposts. The “sorting, search, linking, reminders“ features you initially mentioned are all easily available elsewhere. A highly specific Obsidian-specific workflow is harder to replicate, but everything you initially mentioned is pretty basic functionality.
The features may be available in the new app, but your existing setup will break. Your existing relations and notes will break if they used any Obsidian specific feature, of which there are plenty. Any notes you use to dynamically summarize/organize/sort/filter other notes will break, and probably can't be trivially recreated in whatever app you switch to.
The most basic type of links, links to other notes, will generally work fine yes. But what about links to headings? Links to blocks? Links to attachments? Embedded blocks? Embedded files? The more you've used Obsidian's features, the more stuff will break.
Searching by tags is trivial. What about searching by properties? By done/undone status? By note attributes, by tasks, by attachments, by block-level searches? What about filters?
The simplest use-case being, if I simply want to view the list of all undone tasks across a set of notes on a separate app, sorted by priority, as I can now on Obsidian? Not trivially possible, as far as I know.
Reminders and any calendar-like functionality are definitely not carried over across apps, either.
Like I keep saying, if you limit your functionality to just markdown basics, it'll work fine. Start using the exclusive features of the app or even just the tasks plugin and it's no longer so simple. Something like the Kanban plugin is just impossible.
Not sure I understand your point. There are pros and cons to open sourcing something - should we begrudge the Obsidian team the right to make money from their software, particularly when they’ve taken steps to ensure data portability? And saying that the advanced features the Obsidian team built won’t work without Obsidian is sort of circular, isn’t it? I reckon being able to walk away with your data gets you 90% of the way there.
Nobody owes you an open source text file-based note-taking app with advanced backlinking features, etc. Perhaps you’d like to set up an open source project yourself supporting Obsidian-like advanced functionality?
Open source != Free != Libre, I didn't expect to need to make that distinction. And of course, Obsidian is free to do whatever they want to do.
But primarily, my intention is to to advocate support for and investment in ecosystems/features around open-source alternatives like logseq and AppFlowy, and to discourage investment in the Obsidian ecosystem of plugins, primarily because of lock-in risk.
