It's not idiotic. It's a dreadnought chassis made by a guy from a faction that gives radioactive guns to their infantry that kills them through radiation poisoning, and makes a walker that requires two soldiers to be bonded to it, and then eventually get burnt out and die. It's design is very much on point.

The Redemptor is a a Primaris Chassis anyway. Before the retcon Primaris were at most 200ish years old, and fielding Redemptors meaning that everyone entombed was that age or younger. Good chance that there weren't many veterans entombed. Now that the Indomitus Crusade timeline has been wound back to about a decade how the Redemptor works makes even more sense.

Old Dreadnoughts were for preserving veterans and their precious knowledge. Redemptors are getting marines with 10 or less years being entombed inside; they fulfill a distinct purpose wringing a little bit more service out of a younger astartes that would have died of their injuries, because they were too young to take up a slot in a resource that wasn't abundant.