There's no such caste system at Google. SREs have the same bar as the SWEs, and plenty of people switch roles from one to other. SREs are also well-respected and I don't think anyone would consider them as _not_ real engineers.
> Designing a resilient, scalable, frugal, operateable architecture of load balancers, servers, caches, queues, dead letter queues, and all their associated metrics and alarms is absolutely "real engineering" and worth the time and attention of the same engineers that are building the core business value of their company.
You are absolutely right and that's why having people focusing on that is _really_ important. Having worked at AWS previously, I can tell you that when you force your software engineers to do everything and promote them based on _what_ they deliver without caring about the operational load, you end up with crazy oncalls and poorly-designed software. There's a reason why AWS oncalls are infamous whereas Google's are not.