Of course it should have happened a long time ago. (This kind of thing seems to have actually been most popular in the 1970s, but the first big publicity about global warming and the ozone layer happened in the 80s when policies and attitude trends were very much against the sort of shift you describe.)
Partly I'm cyncical - yes, it's desperately needed and long overdue, but thinking people won't unless forced to by government policy, and not many would vote for that.
BUT something does seem to be shifting this year. It focuses on a small number of areas and can be simplistic and therefore seem almost faddish (e.g. veganism; reducing plastic usage - yet related issues like tetra-paks being harder to recycle than plastic bottles get drowned out). The sudden policy shifts towards electric cars are very interesting; they don't seem to have accounted for the resource shortages for battery production - maybe it's tacitly assumed fewer people will have cars - but more governments are evidently starting to take the idea of peak oil seriously.
I daresay what you say will happen, but again, like the above, a bit too late.
There are cultural issues too - e.g. as was discussed on some of the boards last year, a bit broad-brush, but to summarise, people from middle class backgrounds being happier to have second hand goods.
There will be a certain percentage of people who could make the shift more easily if there were campaigns and publicity, and attitude shifts, (I wonder what proportion?) but there would still be those who are collectors and hobbyists in various areas who'd still be solidly into their material stuff.
It's also difficult economically: environmentally we need degrowth, but how would you manage it politically in a realistic fashion? People don't need the quantities of, say, fast fashion clothing, or new phones that are imported every year, but as well as consumer demand there are a lot of jobs dependent on these things.
I agree about population, but whilst some changes could be possible relatively quietly (e.g. health service not refusing sterilisation to anyone who requests it), would it be possible to make it seen as better to not have kids or only have one kid, without sparking bullying towards larger families? The UN only last year added rights to have children to one of its charters - the conversation is going the wrong way there. There are lots of subtleties going on as well, the way news and government these days talk about "families" rather than "households" or "people" - things like this further cement the idea that it's the default thing for adults to do, to reproduce.