The way I see it, the average guy has a couple of options to feel better:
1)Focus on how bad everyone else is. Many, many people and entire nations truly don't give a rip about intact ecosystems, and never will.
2)Try not to think about it too hard, because it'll never stop. You could drive yourself insane with environmental math.
3)Some combo of #2 and doing some things that really do make sense, like buying used gear, kids clothes, etc. and maybe forgoing some luxuries just for the sake of the exercise.
"Greenwashing" is obviously frustrating because of the hypocrisy. I have yet to be recycle-shamed by someone who is living anywhere remotely close to "naturally", and usually live less simply than I do -- not that I set some wholesome high bar. I just smile and nod.
Less humans would help some, sure, but there are about 1.5 billion people who don't feel that way for religious reasons, and plenty more who don't just because of their own personal or cultural ethos. When we tried to tell some folks of a certain ideology that they had to pay for their grazing fees they forcibly occupied a wildlife refuge. Try telling them they can't have more kids haha.