Well their plan will ultimately backfire on them when they no longer have to vote for a Democrat who is a citizen. Then they will be locked out.
It also backfires when the imported “replacement Americans” want something better than a welfarian existence; enough of the imported Hispanics in Florida supported Trump for him to carry the state. Dems were trying out their national strategy on the state level there, and as one of the liberal talking heads said late on election night 2016, there ARE more Hispanic voters in Florida, but who did they vote for?
Illegal immigration doesn’t play well with people who spent years doing everything right to get here legally - from anywhere.