I'm for it. I frequent open space on public land where people shoot clays. It's not one managed range, but people just shoot wherever there's a hill or canyon to throw clays off and where they're distant enough and screened from any houses. I see waste from shells, clays and wads. The clays are just clay, so they eventually break down despite being the most visible waste because of their orange paint. The brass and polyethylene shells don't break down for a very long time, but at least some portion of the shooters have the courtesy to pick them up. It's not practical to pick up the wads. The felt wads from long ago would break down, but the LDPE wads that are almost universally used today will stick around for decades.
I'm not really concerned about self-defense or big game, buckshot and slug loads with non-biodegradable components. It's the cheap stuff that people shoot in high volume. I have it myself. I bought a few hundred rounds and then some when ammo was very cheap (Federal and Winchester 20ga, $4.69 for box of 25, local so no shipping) for when my boys are interested in shooting shotgun, probably next year. We might shoot it at a managed range (a Trap and Sporting Clays range where all the 4H kids go for shotgun), but we'll probably shoot some of it in the canyons. We'll pick up our shells, but the wads will be out there, and the lead. If Olin and Vista made cartridges with felt and steel without a premium price, I would shoot those for sure. It's not like I need high performance for a clay disc. Yeah I know the steel will scrape the barrel and scour the choke without a cup. I can't expect cheap bismuth and I don't have a solution to all the problems. I don't blame other people for what they do. I just hope we can find a better way for everyone.
I used to reload my own shotgun shells. If I did that again (presently I don't have the equipment), I would use felt wads. Since I pick up my shells to reload them, I'm less concerned about those but I like the all-brass shells because they look cool. I use only steel shot to shoot birds just because I don't like eating lead. I could afford bismuth of hevi/tungsten for game loads, but steel works fine. I'm not shooting turkeys.