It was a personal statement, that's not gatekeeping. A more detached way to make the same point was that D didn't succeed (in the sense of market share) because it didn't reach "far enough" beyond what could already be done with C and C++. It brought real features to the table, but not "killer" ones. Rust did, which is why it's everyone's favorite new toy and why it's been largely (but not entirely, c.f. the linked article) forgiven for flaws like slow build times.