Modern Java is definitely pretty good. But indeed, Java has solidified a lot around "old" style code: making your 50 years old CTO start using collectors and typing `var` instead of MyObject object = new MyObject(); can be a difficult thing. Modern Java is truly quite pleasant.

Kotlin is a fully JVM compatible language. Java is catching up to it in some points (Project Loom has made multithreading in Java almost as pleasant as coroutines in Kotlin), but the experience in writing DSLs, code with lambdas, the brevity afforded by Kotlin makes it more pleasant than java. It's also the default recommended language for Spring/Spring Boot now, that is probably the largest JVM API backend project that ends up being used by default.

The benefits you get are:

* Probably the most stable platform you're ever going to get: the JVM is rock solid and does not require tuning honestly, unless you're trying to get a free few percents of performance. Your shitty SaaS startup doesn't need to do that.

* Probably the most performant JIT in the world. Python isn't nearly close, and Go is close by. Except that you get a good GC with the JVM. Or rather multiple GCs depending on what you really want: throughput/low pauses/etc.

* The packages are truly a massive thing. The APIs aren't always perfect, but behind python & js, it's probably the most fully fledged option.

* Publishing modules doesn't suck.

* Having to carry a jar around does suck a bit, but fat jars solve the problem, and if you're serious in your work, you can just GraalVM it and you have an AOT compiled executable that works great.

Negatives:

* It's java, man. It's still the same verbose beast. Doing low allocation work is a bit hard. Kotlin makes it better. Kotlin also has kotlin multiplatform with a large and growing API surface, and is probably one of the most pleasant multiplatform options, allowing you to delegate to any platform code you want.

* You're never getting a tiny 5MB executable. If startup time is an issue, work hard on GraalVM.