immediately in this case is 50 years

Well, PV costs have declined by nearly three orders of magnitude since they were invented. You now seem to be arguing that unless a technology is mature right out of the lab, it is worthless. You aren't arguing in good faith here.

Not really arguing at all, policy and lifestyle changes could do it, but we’re obsessed with growth and technology. We won’t live with less so our solutions always rely on making more. We’ve missed several climate change milestones waiting for technology to save us.

What we've been waiting for is technologies improving to the point that the cost of using them is considerably less than the cost of not using them. This is how local air pollution worked: the Clean Air Act could be imposed because the cost of pollution control measures was much less than the cost of letting pollution continue. Ditto for the (perhaps more relevant, because it's global) control of ozone destroying emissions.

Right now, in the US, we're using CO2-emitting sources on the grid mainly because of sunk costs. Almost all new generating capacity is renewables. Motor vehicles will reach this point soon, if they haven't already. Technological advancement enables social change, it's not a distraction from it. What you should be arguing for are policies that accelerate the maturation of these necessary technologies.

Sure, but I still think it's true that we could have done this without the technology if we had a functional Senate in the US and the stomach for small personal lifestyle changes. It's kind of silly that we don't. California could stop wasting huge amounts of water on almond farms, for example. We have more fuel efficient cars, but Americans are also driving larger cars than ever. We could stop buying bottled water in plastic bottles, but sales are higher than ever.

Our use of renewables has increased significantly, but the use of fossil fuels has increased more over the same time period.

This is a fair point: if we ditched car centric urban planning and were freer with capital for experimental projects like tidal lagoons and so on, we'd have achieved much of what we need to do.