Why are database features being ignored, and instead reinvented in the middle tier?

First off: any developer using an ORM is naive if S/he thinks using an ORM negates having to have SQL skills. Most ORMs that generate SQL vary the SQL emitted depending on how the object queries are constructed. The developer will need to analyze the SQL to see if they should change any of the object queries.

Short answer: A lot of those features aren't practical for OO development. I know that DBAs don't like to hear that but, it's the truth. Those features are good for edge cases and most good ORMs such as N/Hibernate allow you to provide SQL for those edge cases.

When it comes to being mostly delegated to CRUD:

Long answer: I think the RDBMS world is going through maturity growing pains, and is finding it's place in the world. Truth: OOP is older than RDBMS. OOP is just getting out of it's growing pains and maturing. I think SQL as a language is very mature, but the idea of what a RDBMS should handle is just getting settled. The RDBMS was the business logic holder for most web apps until Java and C# came around. I think we are just starting to feel this correction now.

That being said, I don't think any ORM designer is going to tell you that the quality of the sql statements fed to the RDBMS don't matter.

When it comes to non-CRUD
I don't have an answer here. Most shops I know of still use the DB for ETL/etc...