According to the statistics reported by https://www.codingvc.com/which-technologies-do-startups-use-..., Java looks like the fourth most commonly used language in the startup world, and its usage is not particularly well correlated with success.
Both Ruby and Python are more popular than Java, AND are better correlated with how good the company is. Your odds of being in a successful startup are improved if you are in those languages INSTEAD OF Java.
What about from the individual programmer level? Triplebyte did an article about how programming language and hiring statistics correlate. My impression is that their programmers are mostly being hired into relatively good startups, so it is a pretty good view of the startup world. That article is at https://triplebyte.com/blog/technical-interview-performance-....
Long story short, Java was the #2 language that programmers chose. Behind Python. Not so bad. But choosing Java REDUCED your odds by 23% of actually getting to a job interview. And for those got to a job interview, it reduced your odds by 31% of actually getting hired. By contrast Python IMPROVED those same odds by 11% and 18% respectively.
Apparently the startup world doesn't like Java developers either. You'd be far better off with Python.
Now I'm sure that you can trot out every successful Java startup out there. And there will be quite a few. But based on available data, not opinions, I did NOT express tunnel vision when I said that the startup world stays away from Java in droves.
You may have your own case of tunnel vision. I mean, sure, there are "droves" of startups that stay away from Java (many only to turn to it later), but there are also "droves" that adopt it from the get-go.