weight is great when it's straight and flat.
I'm a heavier rider and i kill on rolling hills, flats and headwinds. Top speed sprints i'm fast and anything with a little down and i'm a rocket.
Uphills are where weight comes into play. For every pedal stroke you'r pushing the bike's weight against gravity. Even with a little speed you still fight it's mass.
For flatter courses heavy matters less than stiffness, power transfer and aero surface.
That's why tri bikes are super aero, yet very heavy.