There are interferometers that fuse the images produced by multiple telescopes and achieve a resolution of 0.001 arcseconds. With changes, couldn't these observe the Moon landers? Is the reason why nobody is seeing the Moon landers related to effort and not actual technical limitations (besides atmosphere interference, brightness, time use, and other general issues)?
Is seeing the apollo moon Landers via earth telescope that hard?
Yes, it still is.
If the resolution of an interferometric telescope is really 0.001 arcseconds, that translates to 4.85E-09 radians. At a perigee of 362,600 km that's 1.8 meters.
top part lower half of the Lunar Modules (that remain on the surface after the astronauts leave) is about 4.2 meters wide which is a little more than double the resolution, so if there is some good contrast then it might appear in a reconstructed interferometric image.
However, those optical interferometers are not designed for imaging of extended objects. They only have a few telescopes and so are mostly limited to resolving more than one point-like object from each other, such as a double star or a star and an exoplanet.
With so few telescopes in an optical interferometer, a complex image like lunar terrain would be difficult or impossible to reconstruct without a model. For example, the images of the accretion disk of a black hole by the event horizon telescope required some input modeling to interpret the interferometric data.
Near sunrise or sunset however, the shadow of a lunar lander will be much larger. The lander is about
7 3.5 meters tall, so the shadow could be 4 or more meters wide by several tens of a dozeon meters long. Since the Moon's orientation, as well as that of the lander and the local terrain is extremely well documented, then at each moment you could estimate what the shadow would look like in size, shape, and orientation. With that model, an interferometric image based on a few telescopes could be used to confirm the shadow.
However, using a model like that won't appease conspiracy theorists.