There's plenty of nuance here, but I must say I am a bit surprised "the tech industry was a contributing factor to SF's decline" needs to be explained in this much detail. With that said, a few points:

1. As you said yourself, no city was a paradise in the 80's in the US for many reasons, and SF, regardless of a massive tech influx, would have risen with the same tide many other cities experienced from the 80's to now.

2. There's an implicit implication here that if it were not for NIMBY's, all of SF's problems would be solved. While I think they would be better, there's a lot of challenges with building housing that fast even outside of zoning. SF has a severe lack of density to start with that would cause issues even with aggressive construction. It's also not a large land area. Compare to NYC who had a huge land area that had way more density. NYC is not an exception here, you can find at least more density or land mass for most other major cities that helped alleviate the problem even with a NIMBY population present.

3. I think again, you're separating the tech industry from NIMBY's when there is much overlap. Many early tech workers wanted the picturesque victorian style house and helped to enact the problematic zoning themselves.

4. The larger thesis here is that the companies coming is a gift to the city, which I think completely ignores the social factors. People come to cities for the people as much as the jobs, sometimes more so in the modern era. It's why NYC has had no problem bouncing back in even the past 6 months despite many offices remaining empty. The decline of SF is very much highlighted by the past few months not seeing the same effect there yet.

5. With point 2 and 4 in mind in particular, it's hard to make a case that first it was a reasonable expectation for people, the flawed beings they are, to simply rebrand/build the entire city to accommodate the incoming industry, and second that even if they did it would have done anything more than slow the decline. Heck, the drastic cultural shift could have even killed it faster.

There are again complex reasons for this, but one of the patterns that is somewhat unique to SF due to the bay area is that you have people commuting out of the city rather than into the city often given Mountain View, San Jose, etc. That adds even more housing pressure on the area compared to the jobs in SF proper. Add in building constraints around earthquakes and the large set of towers in the SOMA / Financial District, and that recipe for disaster is going to be hard to avoid.

Hindsight is 20/20 and no single tech company caused this, but at the end of the day I just don't think it's a stretch to say that a big influx in tech companies was a big part of killing SF and we may have a much better version of the city today if that influx was moderated or even was not there at all. A monoculture of any industry is not good for a city. Cities exist for humans, not economic purposes. They are powered and somewhat caused by them, but a city does not have much value to me if it doesn't serve the people who live there primarily. There's lots of urban theory to back this up looking at company towns and the like.

I've posted about this general thread before here, and I fear the tech industry has not learned its lesson and is simply moving on to another city to slowly squeeze the life out of: https://news.ycombinator.com/item?id=26563775