In my experience working in large Java shops for over a decade this is almost never true. Many Java developers are mortified by JavaScript and typically prefer Angular framework because it imposes a bloated OOP MVVM model that Java developers find more familiar. CSS is like fatal kryptonite (Superman poison) to most Java developers.

This could be why that employer is not happy with the quality of candidates. They are forcefully imposing Java with an iron fist and wondering why people aren’t thrilled to work fullstack like that, when most people are not thrilled to work fullstack like that.

Considering we have only gotten a handful of cover letters, we are having to go by the resume. So if your resume has no Vue and/or no Java, we're forced to read between the lines and guess that there's a reason. Not so much an iron fist, but 95+% of resumes don't convey any passion, so it's hard to say this guy has a passion that will translate to Vue+Java.

Anyone with half a brain can pick up vue in a weekend. Your problem appears to be a complete disinterest in investing in new hires.

So you're saying that someone who likes both OOP and Javascript and more functional-style programming could be a sought after candidate?

Sought after candidates is not how software hiring works. Maybe start ups flush with cash are an exception, but for everyone else hiring almost always is dominated by perceived compatibility more than anything else, even more than utility need.

That is because there are smart people in the world that can self educate and jump into new technology with minimal friction, but those people are rare. Most employers want employees as early as the position opens and they don’t want to invest in training. Java is super desirable to employers because many developers are taught Java in school, it’s single paradigm, and it’s terse OOP conventions force the vague shape of a uniform architectural style. Most developers only know enough to be hired and not enough to write original software, of any style, so employers have to account for these things as though everyone is a junior developer, least common denominator.

That line of thinking suggests lower expenses, ease of candidate selection, and a wider candidate pool. In reality it tends to result in a less qualified larger labor pool with greater insecurity. This is why everything on the JavaScript side is about giant frameworks and the software is super bloated, because putting text to screen is all that matters but nobody knows how the technology works without a framework.

I agree with this observation. I often assumed it would be an USP if I highlight that I want to understand how things work instead of blindly following paradigms and frameworks, but it seems that (a sense of) uniformity just comes with too many perceived advantages, like you said.