James Webb can't resolve Earth-size planets around Sun-like stars. Not just because of the contrast but also because of the diffraction limit. To do that you need a mirror of 20+ meters. But what if you increase the size in just one direction? You get the required resolution but keep the mirror relatively small and easy to transport. This is the idea behind the Rectangular Mirror Telescope.
Watch the video here (with no ads) or on YouTube: https://youtu.be/w3QXTW6DaIg
Universe Today Podcast