Oh it's a real problem alright.
Having used many notes apps & formats over the years, I've been burned by this notion too many times to ever fall for it again. Exporting is only a practical means of migrating sizeable note collections if the export and subsequent import into another system can be done with high fidelity for both content and metadata. This is extremely rare. In practice, the exported version nearly always requires an amount of reorganisation work that's impractical if you have years' worth of notes.
I'll never again use notes software that uses an opaque storage format. In a way I regret this, as it precludes Onenote, Evernote etc, which do have their advantages (no note app I've tried has ever had as nice a basic canvas as Onenote, for example). But longevity and cross-platform availability are the keys for me.
I would have love to put my colleague note on our internal slack, the html export was the closest thing I could use but in practise the generate code is so crapy that it's wasn't possible without spending a lot of time cleaning up the mess and nobody were able to properly find something in his many years worth of internal knowledge base.
That's not a real problem, you can export onenote to many other doc formats. https://www.howtogeek.com/howto/22679/beginner-save-your-one...