As others have said, my impression from local cycling in East Anglia, over the last few years flytipping appears to be getting a lot worse.
But, I can see contributory factors beyond just more people dumping more rubbish. Where it is the land owner's responsibility to clear, that local Council run tips seem to be getting less convenient to use and/or charging might mean landowners leave flytipped rubbish for longer.
Councils seem to be slower at responding to reports (meaning more sites with fly-tipped rubbish sitting sometimes for ages. Some time back I reported a load of domestic furniture (chest of drawers, double matress, double bed, etc. in a ditch and it too the Council over 1 year to remove it.
It's no excuse, no justification but that local Council tips are now so much harder to use (eg my local one tried to charge me last time I went there just some DIY timber offcuts as they recycle, just in my small hatchback, no van), only cash, no receipts. I refused so they allowed me to put in their timer recycling bin anyway. Another I have used near where parents used to live you now have to book a time slot online in advance. All extra grief encouraging those how "might" to become those who "do"
I'm sure more rubbish is being tipped more often but there might be agravating factors.