Thanks for your feedback Chris! You're spot on, others gave similar feedback, and I had similar thoughts to you.
Initially I had a more dynamic rule: First garbage shows up in a dice roll from the previous round, then second garbage shows up at random, then you roll for where the garbage will show up next round. It proved... meh. Unnecessarily complicated, cognitive load for rarely any payoff. Switching to 2 random rolls made the game faster and cleaner. I'd maybe see some exceptions, e.g. 'when a muddy square is rolled, another muddy square gets garbage', but the default random rolls seems to be the way to go for now.
As I said in a different comment, the '6 upgrades per player' was an afterthought because playing only for clearing the field was too long and boring. If you have a different suggestion for a winning condition I'd love to hear it.
I have to admit that I kinda had in mind to make a Legacy PnP game out of this, where stages and upgrade options are different every time, the mud spots stay there and become more and more, garbage in muddy spot need a 'Gloves' upgrade to be picked up, bins matter etc. I didn't have enough time to plan all that, so I just made the default game to get a sense out of it. The ideas you threw would fit there perfectly :)
Thanks for playing, glad you enjoyed!