Re-entry vehicles on ICBMs are moving extremely fast, and aren't really maneuverable in the sense you're thinking. They're not designed to dodge ABMs so much as

Re-entry vehicles on ICBMs are moving extremely fast, and aren't really maneuverable in the sense you're thinking. They're not designed to dodge ABMs so much as hit multiple targets from a single ICBM. Even if you could somehow add high maneuverability to a MIRV, it wouldn't be close to matching how well an ABM can maneuver.