That's not immigration policy, that's mismanagement of funds and constituent resources. He absolutely fukked the migrant response (They are NOT illegal) up by saddling the south side with them and finding all kinds of creative funding to do so. That put him terribly underwater.He let illegal immigrants take city resources that should have went to FBA/ADOS.
He was an idiot for blatantly doing that and losing his Black base.
The main reason he is unpopular though is he was a pie-in-the-sky progressive who came in making all kinds of promises when he had no solid political background. He comes in, wants to do a ton of shyt, but faces the reality that a bunch of Chicago's cash was coming from Covid funds. He has basically been in a stand-still not doing anything substantive since he came into office. Most of the migrants are gone and those who are left are either waiting to get booted via court order OR are on the streets. His main issue with black folks is that he hasn't delivered anything in the meantime and it seems like hes gonna run out the clock doing nothing. 2 years after the migrant crisis was at peak he has done nothing else. Thats the major issue with the black population.
Again, the migrants that are/were here in Chicago are/were here LEGALLY, sent by Texas, and its not free to send people back out. It was a rock and a hard place and Johnson chose all the wrong moves.