I'd argue that it has failed in some organisations. DevOps for me is embedding the operations with the development team. I still have operations specialist, however, they attend the development team stand ups and help articulate the problems to the developers. They may have separate operations standups and meetings to ensure the operations teams know what they are doing and share best practices. Developers learn about the operations side from those that understand it well and the operations experts learn the limitations and needs of the developers. Occasionally I am fortunate to discover someone's that can understand both areas incredibly well. Either way, this results in increased trust and closer working. You don't care about helping some random person on a ticket from a tream you don't know. You do care about the person you work with daily and understand the problems they have.

If you can't account for someone spending x% of their time working with a team but for budgetary purposes belonging to a different team then sack your accountants.

DevOps,like agile, when done correctly should help to create teams that understand complete systems or areas of a business work more efficiently than having stand alone teams. The other part of the puzzle is to include the QA team too to ensure that the impact of full system, performance and integration tests are understood by all and that both everyone understands how their changes impact everything else.

Having the dev team build code that makes the test and ops teams life easier benefits everyone. Having the ops team provide solutions that support test and dev helps everyone. Having test teams build system that work best with the Dev and ops teams helps everyone.

Agile development should enable teams to work at a higher level of performance by granting them the agency to make the right decisions at the right time to deliver a better product by building what is needed in the correct timeline.

DevOps and agile fail where companies try to follow waterfall models whilst claiming agile processes. The goal with all these business and operating models is to improve efficiency. When that isn't happening then either you aren't applying the model correctly or you need to change the model.