In my experience technologies that were popular in the past but are basically dead now are a red flag. Perl, Pascal, Smalltalk, maybe even Java and C at this point, if they don't know anything newer.
Java is an "it depends". Are they writing early aughts style enterprise Java, following early aughts patterns, and using early aughts frameworks? Or are they using fairly modern Java, doing things in a fairly modern way?
I've hired for Java roles in the last handful of years and this was a very bimodal group.
