If you aren’t using a sub viewport/canvas group then that is the solution- match resolutions, do not scale. If you need to scale images down below half-resolution you should make use of mipmaps.
If you are using “Viewport” window settings that may prevent some solutions from working, same with a SubViewport.
What does your scene tree look like? Where does the scaling happen?
Here’s another topic on shrinking textures resulting in artifacts, the solution being mipmaps.