Cleaning coils and compressor

It has what looks like fiberglass insulation under and on the coils on bottom/front.
It is stuck to underside of coils. There is also the same under the compressor in the bottom/rear.
I seek your opinion. Is it more likely that it is just a terrible mess of dust and pet hair?
The more I look at it the more I think it is actually fiberglass insulation.
Should I just brush and vacuum out everything around the coils?

If it is fiberglass insulation what would be the result of removing it and not replacing it?