Without plastic modern consumerist society as we now experience it wouldn't be possible, as such, that party-goer from the movie The Graduate was very correct in the assumptions he made towards the end of the 1960s.

Which is to say, are you sure that the current powers that be are ready to withstand the backlash of their political constituencies once that consumerist policy is actively reversed?

The consumerist part of society may not be capable of generating as massive of a backlash as you might think. The key is in the name. :)

People will do the next convenient thing, whatever it is. Re-use containers made of sustainable materials, not buy something on a whim that they do not need, pay more for plastic as an indulgence (obviously it should not be banned, just taxed), etc.

Also, not a psychologist, but I reckon if you dig into what drives people to exhibit consumerism I suspect you’d find things like 1) wealth/status signaling, 2) virtue signaling, 3) just socially having a good time out with friends (shopping is common), 4) stress relief. None of that would be substantially hindered even if disposable plastic is banned outright (which is perhaps a questionable strategy), it would just find other avenues for expression.

Cases where plastic does enable some things that are otherwise infeasible I believe are numerous, but drink containers is not one of them.