Compliance does not make a frame 'slower' in any meaningful sense — the vertical deflection involved is orders of magnitude smaller than pedalling forces. What it does is reduce muscular fatigue from high-frequency vibration, which on rides over 3-4 hours materially affects late-ride power output. Modern endurance road bikes (Specialized Roubaix, Trek Domane, Cannondale Synapse) build compliance into the frame; more aggressive race bikes rely more on wider tyres and flexible seat posts. 30mm+ tyres deliver most of what compliance frames aim for.