I don't use it, nor do I drink alcohol, smoke tobacco (or vape), and I don't use any other drugs at all. I haven't, for decades. I'm no fun at all.
That's because I burned through my quota by the time I was eighteen.
As far as I'm concerned, they should totally legalize it, to the same extent as booze (which, if discovered today, would easily be classified as a Schedule IV narcotic).
Here in New York, we had the Rockefeller sentencing laws in the 1970s. There's people still in jail, today, for offenses that would get a slap on the wrist, these days.
I doubt that it will suddenly make America look like the parking lot of a Grateful Dead show. People who would have problems with legal weed, are already having problems with it now, or are having problems with other drugs (like booze). Most folks won't have any real issues with it. Some will have problems that will cause things like traffic fatalities. Big Tobacco will take over the industry, destroying many of the mom-and-pothead dispensaries that we have now, and we'll probably see an "artisanal cannabis" industry, like the wine industry, today. I suspect that Napa Valley will become known for things other than wines.
Personally, I think it could be pretty cool. It will be another industry that would promote "back to the earth" values, like farming (except for the inevitable factory farming).
If we were really concerned about protecting people's health, we'd still be in prohibition, and tobacco would be 100% illegal, as would whole classes of junk food.