It's not about timescales, it's about technology. We're sophisticated enough to maintain populations in pretty much every environment at this point, albeit at greater cost depending on which environment.

As for quality of life, those unwilling to adjust their expectations will filter themselves out. There are plenty of anti-natalists on Reddit proudly proclaiming they'll never have kids because the world already sucks too much. Well fine, but don't think everyone's going to go that route. Humanity got by for most of its existence with essentially no economic growth or quality of life improvements. Would suck to go back to that, but the species would continue.