> This might be just over-familiarity on my part, but does SQL really have a strong learning curve, or is it just not used often enough directly these days that people can get by without knowing it?

I think the problem is that it's declarative instead of imperative, which is really kind of a shock if you are not used to it (you can't go step by step, there's no debugger, there are no branches etc), and also that you have to think in sets in terms of your solution, which is also awkward when you're not used to it.

I think it's definitely worth it though, as nothing we have beats the relational model for CRUD, and there are so many great learning tools online, for example: https://sqlbolt.com/

SQL has a large learning curve, you can keep learning new thing on it for ears. But not a particularly steep one, you can start using it with very little knowledge, and anything extra your learn immediately improves your situation.

> does SQL really have a strong learning curve

Depends. It's easy if all you want to do is select * from whatever;

When you get into subqueries and a whole ton of joins to get the information you need, it can get pretty complicated.

I mean, we have a full university course which was 80% SQL, spanning 6 months.

TL;DR the language is not complicated. Actually using it, can be.