Well, for one reason, racoons, ducks, snakes deer and possum do not require human depopulation (or prohibition of human settlement) to survive. Besides, none of the animals you mentioned, with the exception of the four poisonous species of snakes in North America, kill humans.
But at least snakes keep the rodent population down. What contribution do the relatively limited numbers of grizzlies make to the eco-system?
I would argue that the price of keeping grizzlies in the lower 48 is too high when considered against the economic costs to humans of the Endangered Species Act -- which essentially gives the government de facto control over every square inch of United States territoty.
Why is it necessary to prevent the extinction of every species on the planet -- especially known human predators -- when species extinction has been a part of the natural order since the first random amino acids evolved into living cells.
Somehow, nature survived the loss of sabre toothed tigers, mammoths and mastodons.
Besides, there are still plenty of grizzlies north of the border.
They're top predators, and omnivores; scavengers par excellence. They clean up the dead and the weak and the excess. I live in Maryland, and we could use a few more top predators around here; deer are a hazard to one's health (on the roads) and one's garden.
Let's introduce them to New York City. We could populate Central Park with them. This would eliminate three problems.... a place for Grizzlies, yuppie joggers and homeless people.