What's the endgame for propping up population numbers with immigration? Surely the whole system falls apart once the net fertility rate falls below 2. What then

What's the endgame for propping up population numbers with immigration? Surely the whole system falls apart once the net fertility rate falls below 2. What then? There's good reasons to be immigration-friendly, but dealing with the endgame of the inevitably shrinking population like the Japanese are doing seems like a better long-term strategy than the temporary band-aid solution of solving the problem in the short-term with increased immigration.