As a recent grad myself, this is the only comment that rings true for me. Anecdotal for sure, but most people that I went to grad school with and stayed in the bay are doing fine, even at mid-size companies. You can find someplace to live (especially with a significant other) that enables a moderate amount of saving / investing with a little frugality; however, there's a lot of luck and privilege that plays into being a successful young engineer in the bay, and in no way do I want to downplay the seriousness of these issues for other groups.
Lots of people stay here despite the costs because of the positive externalities that come with living in the bay. There are many alternatives to a highway commute (bike in the city, Caltrain, work from home) that many new grads are able to take advantage of. There's easy access to nature, culture, and for a lot of people, an extended network of family and friends that probably wouldn't be so welcoming in other places that don't have the same strains on housing.
I expect that many will move away for opportunities elsewhere before ultimately returning, but that seems to be a desire for exploration rather than dissatisfaction with quality of life. Certainly, few of the people I know are itching to leave the city for even low-density suburban living, and that's a preference that just can't be squared with many of the commenters here that rave about living on their 3 acres of land for $200k in the middle of nowhere while working remotely.
There are a lot of problems in the bay (and even more in the city) that I hope we can address, but making it out to be unlivable for young engineers (again, a very privileged class) is ridiculous. Are there better places to raise kids? Yes. Are there cheaper places to live? Yes. Are there other urban areas that provide some of the same benefits? Yes. Do I want to live anywhere else? Not right now.