I don't argue for a second that our birthrate isn't dropping; it is. But we either haven't dropped it enough, or it's being offset by higher consumption. The overshoot day is now the 1st of August [1]. Until we push that back out to to a sustainable level, we haven't done enough.
To achieve that, I can only see a few classes of solution. We could reduce our per-capita consumption, our lifespan, or our number.
I'm assuming that the overshoot day is roughly correct. The details of exactly how much our birthrate has dropped or by how much our consumption has increased isn't important to know that there is a massive discrepancy between where we are and what is sustainable. Doing anything that increases that discrepancy is probably going to make it worse.
I'm very uneasy about us collectively seeking longer lifespans. Earth is already supporting more people than is sustainable. Living longer robs someone else of an opportunity to live, or a shorter life. Over many generations we may be able to lower our birthrate to compensate, but I worry about happens in the meantime.