It's also a stretch to claim that reinforced concrete is even a figurative façade: it's not just concrete over steel beams as rebar alone isn't structurally sound enough either without the concrete. In that way it is considered an "authentic" building material in Brutalism theory and not a facade.

Absolutely, reinforced concrete is not a recommended structural design tool in modern thinking, but some of that is learning lessons from mistakes Brutalists made, so it's hard to fault some of the over-reliance on reinforced concrete.

Just because a lot of Brutalist works seem to be failing at their original goals with at least a couple decades of hindsight, doesn't mean it wasn't worth exploring those ideals and goals. There's a lot Brutalism has taught us/can teach us about building materials, and the public's ever-changing relationship with civic spaces, and even what the "usefulness" of "ugly" buildings can sometimes be.