AGAA4
It has got worse. The country park near where I live rarely had any dog poo left and there was no rubbish but for the last few years I have seen an array of coloured bags left on rocks or hanging in the trees. Drinks cans and other rubbish just thrown down.
I don't think these people think about who cleans it all up. As long as they are rid of it they don't care.
I think some of the the attitude is (being charitable here) that someone is paid to clean it up so why should they...
About 10 years ago I was helping to clear the garden of a large institution which had been empty for some years. Locals had easy access to the gardens and it was well used for dog walking. We had to remove a great many empty poo bags; the contents had rotted but the bags remained.
Quite honestly, I'd rather that the dog poo was just kicked or thrown into the undergrowth where there is some, to rot quietly without trace. Not in urban areas, of course, but in the countryside.
It's a difficult subject though. At least everywhere is, on the whole, much cleaner because most dog owners do pick up after their animals. You notice it if you go abroad to somewhere where people don't pick up. But the plastic lasts for years and years, even if its contents don't; it's not very environmentally friendly.