So, as long as some humans are successfully making new humans, whether or not the rate is exactly 2.3 is irrelevant. World population has been skyrocketing for the past 100 years. It wouldn’t be the worst thing in the world for that to backslide a bit. It can probably go down 5x and we’d still feel like the place is crowded.
The only thing to worry about is some widespread event that affects fertility workdwide. Like what if these micro plastics are really getting into our testicles and reducing sperm counts? They are getting everywhere. If men everywhere started shooting mostly blanks then we would all be in a panic.