So now we have easily come up with three different ways of rewriting the query to avoid that duplication (which obviously was not a problem at all to begin with): subquery, CTE and lateral join. And there are also several more well known ways (views, custom functions, computed columns etc) so the whole premise now for even inventing a "better" language than SQL is then false? Or what am I missing.

It's also weird how people always argue for immutability and eliminating local state, when using procedural languages, but as soon as they switch to SQL, that actually works like this, they immediately want to introduce mutability and local state.