My take is that it appears to be driven by mentality rather than whether somebody is an immigrant or not. People, immigrant or not who like putting in the work end up succeeding while those that complain or act entitled do not. It’s plain as day, nobody is going to give you a hand out so you have to work for it. Welcome to capitalism. It sucks, but get with it or you lose.
I’ve got successful immigrant and non immigrant friends and those that end up succeeding also end up being like minded. That said, I do think that, yes, immigrants more commonly have the “work hard or fail” mindset given their prior socioeconomic status typically ends up being unfavorable which serves as a catalyst for them.
I agree with entitlement becoming more and more common these days but that can also be attributed to people being generally more outspoken and having platforms to voice their concerns.