Like I said interferometers exist but they are very limited in their capabilities. For example the VLT interferometer is limited to observing objects that are brighter than 18th magnitude (and that's using multiple 8m telescopes! Using the auxiliary telescopes which are still 2m you are limited to about 10th magnitude). Something that is easily within the reach of a single telescope less than 50cm in diameter (single 8m telescope can see objects fainter than 25th magnitude - 7 orders of magnitude difference!) - something you can buy for less than 30k$!

Interferometry gives you high resolution at the cost of sensitivity. And there way more things that require high sensitivity than high resolution. And I haven't even mentioned spectroscopy, which is hugely important in modern astronomy. And there is no way around having a big light bucket - I wish there was.

Thanks, this Wikipedia page has more -- and consider adding! https://en.m.wikipedia.org/wiki/Astronomical_interferometer

Thank you for the explanation, I was wondering the exact same thing and I know nothing about optics.