There's now ~2 generations of professional engineers for whom SQL was rarely/never a thing to learn. Between the hard(er) split among front-end/back-end developers, ORMs improving, and the (flawed) idea that NoSQL would make SQL irrelevant, it has become somewhat of a niche skill.
Think about Firebase. One can be full stack on an app built on Firebase and be successful without ever touching SQL. Firebase is very popular, and has been for some time.
Source: I have worked with a set of otherwise solid engineering teams and can say that SQL familiarity has given me a leg up on very smart engineers who nonetheless do not do relational databases.
The only way you can get away with creating an application without touching sql is of you offload the logic to your backend language, and then I don't think you'd be efficient enough to scale.
Also can someone actually understand the logic of joins, indexes, pks, etc enough to create an efficientand scalable db, and not simply have learned sql by proximity?
> The only way you can get away with creating an application without touching sql
Please look at app platforms like Firebase[1]. There are absolutely complex Web applications running at scale that do not use SQL anywhere in the stack.
Aside from that, MongoDB and Redis are 17 years old; CouchDB is over 20. NoSQL is well-established at this point. All of the hyperscalers offer proprietary NoSQL databases, and have done so for years. A large number of developers uses those databases in production.
In our API-centric environment, there are a lot of apps that don't do much in the way of managing their own data directly at all, using mixtures APIs for auth and other key application functions.
> can someone actually understand the logic of joins, indexes, pks, etc enough to create an efficientand scalable db
If you are not using a relational database, these concepts do not necessarily apply.
Think about Firebase. One can be full stack on an app built on Firebase and be successful without ever touching SQL. Firebase is very popular, and has been for some time.
Source: I have worked with a set of otherwise solid engineering teams and can say that SQL familiarity has given me a leg up on very smart engineers who nonetheless do not do relational databases.