I'll try! Last.fm started many years ago, in the early '00s (pretty much like Django!). They decided to use Django to serve their website and API. As the years went by, some issues and limitations started to show up: the API has several quirks they can't fix, the frontend -even after the redesign- is slow, and interactions feel clunky and outdated (like early AJAX attempts).
The API can't be easily modified -and sometimes XML responses have info JSON don't-, the website is stuck on being served through the framework instead of relying on a modern API... They even have an "old" and "new" database for albums, so when you query some of the albums through the API they come back with no tracks because the API is in the old codebase. It's a mess. And from my experience with Django, it feels a lot like the difficulties we had trying to scale and improve our existing code. It's not that you can't do things: it's just that Django isn't agile enough to adapt. You end up adapting to Django and its -beautiful and magical- ways.
Of course we could blame it on poor design choices, lack of Django knowledge or just call it technical debt... but I believe the framework is the major culprit.
For context: I haven't worked for last.fm, but I manage a third-party client (Open Scrobbler). I've been using their API for more than five years now, had interactions with their devs, read many replies in the API support forum and even tried to find undocumented endpoints that could help me (during this time I found some old profiles and test pages where you can even see screenshots of Django logs!).