The U.S. Air Force’s chief of staff wants the service to develop an affordable, lightweight fighter to replace hundreds of aging F-16s and complement a small fleet of sophisticated F-35 stealth fighters. But an affordable, lightweight fighter is exactly what the F-35 was first conceived to be.
Lower frequency VHF radar also inherently isn't really subject to stealth at those sizes. It's not as accurate as other bands, but it's accurate enough to guide a missile in the neighborhood of the plane and have it detect it using imaging IR or Radar.