Why a badly damaged Invincible would not be rebuilt

If a superfiring Invincible survived Jutland with a destroyed midships boiler room, how long would rebuilding the machinery spaces take?

The Royal Navy probably would not rebuild her because the structural and machinery work would approach the cost of a new ship while offering little wartime or postwar value.

A severely damaged Invincible probably never returns to service. By 1916 the class is no longer needed to chase dispersed German cruisers, and the Royal Navy would not expect to retain the ship for long after the war. Replacing a boiler room requires major structural access as well as possible engine and machinery work. Once that expense approaches the cost of a new hull, the ship's remaining strategic value cannot justify reconstruction. The decision becomes an economic write-off rather than a question of repair time.