I don't think life without civilization in the broadest possible abstract would be much worth living (for other species maybe but then one is actually advocating voluntary human extinction at that point).
But I don't think *human* life would be much worth living, but one is going to be all "oh you mean transatlantic travel", NO I mean women not dying in childbirth at massive rates (like I've always said notice it's ALWAYS men advocating this....) But even if somehow it were and we were like "a bunch of women are just going to die in childbirth ho hum, so their average lifespan is 40, oh well", I don't think anyone from this culture can even imagine life without civilization, it's so far out there. So therefore I really think his thinking is a dead end, not just radical but so radical that it can't even serve as an ideal to work toward .. But notice it seems there has been civilization without massive fossil fuel use, what about the Roman empire? Technologically advanced in some ways no? LONG BEFORE the industrial revolution. Not utopia, not without exploitation - in fact slavery, not as advanced as now? No noone says that, I'm just thinking about technology.
But an alternative way of life? Well I think some kind of degrowth eco-socialism might be desirable. Because most of our real improvements to life due to technology may amount to a few things: oh yes modern medicine is one. So I try to read de-growth books to try to understand what it would look like (so I read Herman Daly's Beyond Growth, and I'm maybe 1/2 through Prosperity Without Growth), and I don't know yet, but it seems less of a complete dead end to try to imagine what such a world would be like with technology used appropriately, than just declaring: all civilization is bad.
Of course population is a big factor, if the population of the world was 2 or 3 billion rather than near 8 billion (and that is very recent) this would all be easier to deal with, it's easier to deal with at 8 billion than 12. A better life for less people would be better, but try to tell that to people (and no I don't advocate murder of already existing people, I advocate limitation of birth rates). People who advocate against population growth actually are advocating the EASY way, it is the easy compared to collapse sure, but also compared to trying to limit economic growth without limiting population growth. One can do things the easy way or the hard way.
The problem for solar etc. is we just add solar and keep on using the same amount of fossil fuels etc. because energy use keeps increasing. The problem is growth (fueled by population growth too). At the same energy use alternative energies would probably (eh yea even I don't know for certain as it's a total lifecycle cost thing) reduce fossil fuel use as they would replace some of it. But that's not what happened, energy use keeps growing.
As for big environmental movements? I think you have to be pretty naive and not really paying attention, to not realize most big advocacy things have their corruption, it doesn't mean they are entirely corrupt but ...