There's no good reason that Santa Cruz should specifically stay the way it was 50 years ago or whatever. Personally, I would have liked for Santa Cruz to remain the way it was before people came and tore up all the nature to build a bunch of suburbs, but I can't get what I want either. Culture is inherently ever-changing; Santa Cruz may be _different_ in 50 years if densification and growth was allowed but I don't see how it would be somehow not be Santa Cruz.
There are real, severe economic effects from trying to freeze a city in an arbitrary point in time. At some point the well-being of real actual people needs to be prioritized over the aesthetic preferences and property values of a few NIMBYs. Especially when those aesthetic preferences essentially boil down to hating multi-story apartments and public transit.