I've used Django with "real data", as in accountancy software for multiple years of transactions across 200+ fairly large clients and it's absolutely fine.
Whereas I've used Sqlalchemy and getting it to do a basic join, turns out there's 3 different ways of doing it all with an insane amount of crap to find the right way of doing things. I actually left my old job in part due to Sqlalchemy being too painful to work with.
I use Django with "real data" as well and, generally, it's pretty good once you learn how to wield it. My biggest issues are lack of multi-column primary keys and inefficient queries when doing .count(), that often introduce unnecessary group by statements in the subquery. If either of those could be addressed, I'd enjoy it so much more.
Whereas I've used Sqlalchemy and getting it to do a basic join, turns out there's 3 different ways of doing it all with an insane amount of crap to find the right way of doing things. I actually left my old job in part due to Sqlalchemy being too painful to work with.