It would take a complete collapse of the biosphere of multi-cellular organisms to effectively reset the clock on life and I just don't see that happening. Even our worst-case anthropogenic scenarios, devastating for us to be sure, don't come close to past events. And with the vast numbers of Humans alive, some will survive to form new pockets of civilization. They'll be able to rummage though the remains of our civilization to jumpstart their own development. Who knows, Humans surviving past the 6th extinction might still colonize beyond Earth before the end of the millennium, having access to much of what we have already learned.
This is what really bothers me about doom-and-gloomers. They oversell the apocalypse, which means people get paralyzed by fear or they shrug their shoulders in indifference because there's nothing we can (or will) do. No. This is wrong. We have to prepare for what's coming and ensure as much of what we can of the continuance of technological civilization. We need to face the reality that things are going to get nasty despite our hand-wringing, half-assed attempts, and denials. We aren't going to stop 2 degrees C from happening. We aren't going to stop at 2 degrees C either. We fucked up. We are continuing to fuck up. We will continue to fuck up. All that we can do, because it's much too late to do what we should have done, is prepare for the consequences and try to survive the new normal. Billions will perish but not all at once. Decades of starvation, disease, war. All until a new equilibrium is attained. Some pockets will survive, others will develop as survivors find one another.
I would hope something of a miracle happens that we avert the worst of it, but I think we're pretty much committed to this course and live in one of the darker timelines. We need to be realistic about what has happened, what is happening, and what will happen. And how Human civilization is going to live through it.