The worst part of SQL is indeed how hard it is to compose. Something like D, where you would keep the relational model but add user-defined types would indeed be a strict improvement.
The reason why I'm skeptical of most proposed alternatives is that I'm fundamentally in your exact same position: I know SQL isn't perfect but I'm reasonably content with it; and they invariably all end up throwing away the "good parts" of SQL (relational model, declarative, easy stuff is easy).
The first step of an hypothetical solution that replaces SQL isn't "SQL sucks", it's "SQL is extremely good at what it does but has problems that are only fixable with a new language".
The reason why I'm skeptical of most proposed alternatives is that I'm fundamentally in your exact same position: I know SQL isn't perfect but I'm reasonably content with it; and they invariably all end up throwing away the "good parts" of SQL (relational model, declarative, easy stuff is easy).
The first step of an hypothetical solution that replaces SQL isn't "SQL sucks", it's "SQL is extremely good at what it does but has problems that are only fixable with a new language".