I'd say the zeitgeist has moved along to the point that decriminalization looks backwards.
Just legalize it, and let's stop living this absolute farce that it is anyway harmful to individuals or society.
Eh, no, it still needs restriction like alcohol does. i.e. must be done on your property, illegal to be on the influence while driving (probably exists but those laws will likely need to be updated), don't sell to minors, etc.
On top of that though, we can't just say it's unharmful to everyone. Like with alcohol, someone with certain mental conditions should not be taking marijuana because it may just worsen their state. However, there's no way to monitor someone like that to not take neither alcohol nor marijuana, so perhaps the point is moot.
And I think there should be research on what happens when one takes it daily over a long period of time. Smoking daily or alcohol daily can lead to some eventual health detriments, depending on the individual. Once legalized, that will have to be looked at as well since it's now available to purchase.