I think of Java/Kotlin and Spring as a secret weapon for startups. My workplace was a startup 5 years ago and it's amazing how things just worked as expected, leaving us more time to focus on the product. We have tried a few alternatives over the years, such as a few services in Rust, but the people who implemented those have usually seen the advantage of using a stable ecosystem after a few years. It's unfortunately something you need to experience yourself instead of being told by someone else.