There are quite a few database products and other data intensive systems written in Go, Java, and many other languages. Generally this is much less of an issue than you think. And it's offset by several benefits that come with having some nice primitives to do e.g. concurrency and nice language to work with.
On the JVM you have things like Cassandra, Elasticsearch, Kafka, etc. each of which offer performance and scale. There are lots more examples. As far as I know they don't do any of the things you mention; at least not a lot. And you can use memory mapped files on the JVM, which helps as well. Elasticsearch uses this a lot. And I imagine Kafka and Cassandra do similar things.
As for skillset, you definitely need to know what you are doing if you are going to write a database. But that would be true regardless of the language.
While it is true that Cassandra and Kafka are great software that countless developers rely on to handle massive scale...
It is also true that the JVM and the GC are a bottleneck in what they are able to offer. Scylla and Redpanda's pitch is "we are like this essential piece of software, but without the JVM and GC".
Of course, having a database written in Go still has its pros and cons, so each to their own.
The JVM and GC have a learning curve for the people implementing the database. But most users wouldn't get exposed to any of that. And if you manage it properly, things work fine. I've used Elasticsearch (and Opensearch) for many years. This is not really an issue these days. It was 10 years ago when JVM garbage collection was a lot less advanced than it is these days. These days, that stuff just works. I haven't had to tune GC for at least half a decade on the JVM. It's become a complete and utter non issue.
There are many valid reasons to pick other products but Elasticsearch is pretty good and fast at what it does. I've seen it ingest content at half a million documents per second. No stutters. Nothing. Just throw data at it and watch it keep up with that for an hour sustained (i.e. a bit over a billion documents). CPUs maxed out. This was about as fast as it went. We threw more data at it and it slowed down but it didn't die.
That data of course came from kafka being passed through a bunch of docker processes (Scala). All JVM based. Zero GC tuning needed. There was lots of other tuning we did. But the JVM wasn't a concern.
On the JVM you have things like Cassandra, Elasticsearch, Kafka, etc. each of which offer performance and scale. There are lots more examples. As far as I know they don't do any of the things you mention; at least not a lot. And you can use memory mapped files on the JVM, which helps as well. Elasticsearch uses this a lot. And I imagine Kafka and Cassandra do similar things.
As for skillset, you definitely need to know what you are doing if you are going to write a database. But that would be true regardless of the language.