TL;DR: for optical wavelengths, with typical image sensors that only detect amplitude and not phase of the electromagnetic wave, you need to do some really hard work to ensure optical coherency. For radio telescopes, it's a lot easier since you measure both amplitude and phase.
Another technique that's a lot easier to accomplish for amateurs is lucky imaging:
In this context, it's relevant to note that the VLT was built with interferometry in mind, and they are now getting it to work reliably. See for instance the page about the GRAVITY instrument: https://www.eso.org/public/teles-instr/paranal-observatory/v...