> Nevertheless, as with many frameworks, it gets awkward when you move too far away from the 'intended use cases'

Right. And that probably applies to many, if not all frameworks, by virtue (vice?) of their design. I don't know Mendix, but I've worked on programming frameworks like Rails, Flask and others, including some in-house company proprietary ones. You sometimes have to work around their limitations with custom code, awkwardly, even Rube Goldberg style at times.

And there can be instances or even categories of apps that can't be done using the framework at all.

The framework giveth and the framework taketh away.