Modern astronomy works at the edges of whats possible, a single frame might take hours. Needing multiple frames would mean multiple days per observation. It would mean no longer seeing faint and distant objects, limiting us to younger, closer and frankly far more boring objects. It would make observing variability impossible for certain timescales.

You need old distant objects for cosmology, observing the structure if the universe, big bang and stuff. You need variability for finding exoplanets, measuring distance and observing transitions such as supernovae.

Oh, and then a huge part is taking spectra, which means bouncing the light directly off a grating. Filtering transients is hard to impossible there. You need spectra for relative motion, magnetic fields, composition of matter and radiation and of course temperature.

Needing such filters would set astronomy back a few decades

Hey you're back! I asked you previously "That might work for imaging, but what's your fix for spectroscopy?" here: https://news.ycombinator.com/item?id=21577081

You replied "Optical, RF, or Xray?"

Then I said, "Let's start with optical." but then you disappeared!

So, what's your solution for long-slit optical spectroscopy?

No, they are too bright and will saturate the detector with even very short exposures. Best you can do is just discard the affected area, at worst you have to discard several exposures because the saturation effected the readout electronics.