I'm all for the YIMBY and zoning reform push, but a) that's decided on the municipal level, b) change is slow, c) immigration rates can drastically change in very little time, if the feds decide. In Canada feds wanted to have their cake and eat it too: the population grew by over 3% in a year, but infrastructure at the provincial level (e.g. healthcare) didn't budge, and housing isn't building much faster than it was before.
If we understand that the key factor behind housing affordability is inelasticity of supply, then it should be easy to intuit that other things can be inelastic: policy and the law. By contrast, immigration rate might as well be a push of a button. It's not responsible to jack up the rate first and keep it that way just because it's not "the-thing-that-ought-to-change".
There are of course other externalities with high immigration rates (for contrast, US immigration rate is not that high), and the downsides to low immigration are overstated. Older generations won't live forever, but what I generally see is a call for unnecessary wealth transfer from young generation to old. Boomers are the wealthiest demographic already. We don't need to give them more freebies.