Having been at Microsoft when we had SDETs for everything (and I miss it greatly, though the way we could write a feature and then just toss it to test was ridiculous), I think things have swung too far away.

On one hand, engineers needed to take more ownership of writing things other than low-level unit tests.

On the other, the SDETs added immense value a ton of ways, like writing thorough test specs based off of the feature spec (rather than the design spec), testing without blind spots due to knowledge of the implementation, implementation of proper test libraries and frameworks to make tests better and easier to write, and an adversarial approach to trying to break things that makes things more robust.

I've also worked with manual QA for product facing flows, and while they added value with some of their approaches to ensuring quality - poking at our scenarios and tests, and looking more closely at subjective things - they often seemed to work as a crutch for the parts of code paths that engineers had made too difficult to test.

I've never seen anywhere attempt to replace the value that SDETs delivered with what engineers were tasked with. I'd argue it's not necessarily possible to fully replicate that when you're testing your own things. But with services now, it also seems like product/management are more willing to have slightly few assurances around quality and just counting on catching some in production in favor of velocity.

I've never seen places that got rid of QA