Unless you have crazy custom files I feel like this is a non issue Obsidian is just rending markdown so any potential future app (or the influx of slop AI markdown editors/renderers) out there could do the job albeit worse than Obsidian.

Obsidian doesn't just render markdown though. There's a ton of functionality on top of Markdown which makes switching to any other tool very hard in reality. This is further exacerbated once you start relying on plugins (which arguably is the case with the majority of Obsidian users).