I agree they should have codified it. They had since 1973 to do it.
In the end, I think the dems miscalculated and never thought the republicans would actually kill their golden goose; abortion was a major sticking point for single-issue voters. Hindsight is 20/20.
According to this 2022 YouGov poll, respondents over the age of 65:
Overall, it looks like the plurality (42%) of Americans believe immigration has made the U.S. better. A minority (25%) of Americans believe immigration has made the US worse, and less than that (16%) believe it has not made much of a difference.
So for boomers specifically, it looks like around two-thirds are digging their own grave here.