If I understand you correctly - what you seem to be saying is that actions which require meaningful changes in lifestyle for people in those capitalist democracies rich enough to avoid the worst potential consequences (at least for now) are not going to be acceptable to voters, and they will therefore resist doing what climate activists believe needs to be done. I guess relevant examples would include the current well-organised resistance to Low Traffic Neighbourhoods across London, or indeed the Maillots Jaunes protests in France, where small increases in the cost of fuel led to massive protests across the country.
This is possibly true - I don’t believe it but I think it’s hard to test either way. There are certainly counter examples of where comparatively wealthy countries *have* accepted great costs to do the long term right thing. Again (and I appreciate wartime metaphors are overused…) I think even the most extreme responses to Climate Change will not be as costly to peoples lifestyles as what was endured during the Second World War. Looking at the treatment of the Danube pre 1989 is another example of how capitalist democracies can actually be pretty effective (certainly more effective than any of the available alternatives) at managing common environmental goods.
I would also question whether "economic collapse" is certain. There is certainly an aggressive "degrowth" element in the environmental movement, who seem to take a positive delight in telling people how much harder things are going to be for them. While there will surely be changes, it doesn't have to be a given that they will feel like "doing less" - at least overall. Certainly - we can almost certainly expect to fly less, drive less, eat less meat - but cities which are more accessible by bike, more plentiful and accessible public transport, high quality jobs in emerging industries. And again - I know I keep banging this drum - but it's incredible
JUST HOW CHEAP SOLAR HAS BECOME. I know that many people would argue that it is crazy to just wait until some technology comes along to magically fix the environment - that we have to act decisively and politically now. I agree with this - but it is equally crazy to assume that no technological advances are going to come along. Times of crisis lead to great advances, and the concerted will to do things right now will have huge impacts.
I guess one positive thing about all this is that most likely, what happens on our little island is only going to be of minor importance to anyone but the people who live in our little island. The real story is being played out between the US and China. If there's one thing that the US is good at, it's figuring out how to turn crises into
economic opportunities.