Quite right. I regard both Bluecher and Invincible as failed versions of....As some commentators have pointed out to treat her as a 'failed Invincible' is incorrect.
In comparison with the sadly-never-built Unapproachable, Bluecher is a bit too slow and wastes tonnage on the 15cm battery (no AP shells, so useless against anything bigger than a DD).
If the RN had built an Unapproachable (probably turbine-powered) rather than Invincible, I imagine the Germans' alt-VdT would have been a larger and faster Bluecher, with no 15cm and at least sixteen 21cm.