Depends where you live. I live in a desert so humidity isn’t an issue, but dust is. I keep most of my filament in bags just to protect from dust. The only one I actually vacuum seal is tpu. Pla, pla+, and petg all do fine without. If I store it for more than a year though, I run it through the dryer first. Or at least have the dryer running while I print from it.
Make sure you calibrate your e-steps after swapping hotends. I did the same thing on my ender 3 putting on a volcano hotend, and started getting overextrusion. After adjusting the e-steps it was back to normal.
Check for a partial clog. 80% of the time i get that consistency with petg, its because the nozzle is partially clogged. The other 20% is the ptfe tubing is shot. Usually it partially melts and causes underextrusion.
Wet filament could be an issue too, but this is pretty extreme for wet filament.
A lot of it is stolen, stripped of what the theives want, and then dumped to get rid of evidence. Whatever is left anyway. The rest is simply because it’s cheaper than bringing it to the landfill. Landfill is $12-15 for a truckload. The fine is (up to) $10000 for illegal dumping where I am. Lots of risk, but the likelihood of getting caught at night is so low that it isn’t really a factor. Landfill really just needs to be free for individual residents. The amount the gov spends on cleanups is probably more than their $12.