Where I've seen QA teams most effective is providing more function than "just" QA. I've seen them used for 2nd tier support. I've seen them used to support sales engineers. I've also seen QA teams that take their manual test plans and automate their execution (think Selenium or UiPath) and have seen those automations included in dev pipelines.
Finally, the QA team are the masters and caretakers of your test environment(s), all the different types of accounts you need for testing, they should have the knowledge of all the different browsers and OSes your customers are using, and so forth.
That's a lot for the dev team to take on.