> Also, interfaces are extremely important to allow your components to be easily replaced even at runtime.

The share of all software that actually benefits from this is extremely small. Most web-style software with stateless request/response is better architected for containers and rolling deployments. Most businesses are also completely fine with a few minutes of downtime here and there. For runtime-replacement to be valuable, you need both statefulness and high SLA (99.999+%) requirements.

To be fair, there is indeed a subset of software that is both stateful and with high SLA requirements, where these techniques are useful, so it's good to know about them for those rare cases. There is some pretty compelling software underneath those Java EE servers for the few use-cases that really need them.

But those use-cases are rare.