The suggestion is to try icomplete-mode instead. But icomplete-mode isn't really tuned for buffer switching in the same manner as iswitchb. After some digging, it looks like there was a plan to gradually integrate the features of iswitchb/ido into icomplete-mode, but that hasn't happened yet, and yet iswitchb was obsoleted.
Fortunately, it looks like ido these days allows one to only turn it on for buffers. This will do the trick as a replacement for
Once that's done, you can even enable icomplete-mode safely without having it meddle with buffer switching, so: