The problem is like with JS or PHP, it is ubiquitous in many settings. There are a lot of people who can use it because it was the default language taught in CS programs, many corporate settings for decades, or similar. It’s the runtime for android devices. It’s everywhere. Of course you’ll encounter a lot of low quality developers.

Your comment mostly indicates that you haven’t been fortunate enough to encounter the high quality Java devs, not that they don’t exist. They exist and they build world class software that backs massive systems like elastic search, Kafka, spark, or Cassandra.

The framework was reasonably good for its time. By the time good looking UI frameworks came, the bad reputation was already set.