Don't beat yourself up to much!! I've seen worse!
Heck I removed mine, cleaned it 6 ways to sunday and put it back in!
It seems the OEM material is like nomax sheet material with super tiny holes in it, looks solid but air goes right thru. Then I looked at the aftermarket filter, it looked a lot more porous, so I put the used, cleaned filter back in!!
Inspection inside the ducts showed so little dust for 9 yrs of use, it was surprising!! wow