This is a subject that really irks the engineering side of me. It's utterly ridiculous that engineering and efficiency decisions are so deeply affected by whether or not the largest search engine will properly index your content.
Why is it that Google doesn't get flak for not discovering content that's engineered to send the absolute minimum over the wire, cache intelligently in localStorage and IndexedDB, and scale well by distributing the appropriate amount of rendering work to the client agent? Why can't I expose a (JSON/)REST-API-to-deep-link mapping and have Google just crawl my JSON data and understand (perhaps verifying programmatically some percent of the time) that the links they show in search will deep link appropriately to the structured JSON content they crawled?
It's such a waste of talent and resources to force server-side rendering. There's obviously the resource cost of transmitting more repetitive content over the wire, and requiring servers to do more work that the client could do. (Yes, even with compression this will still be a higher cost, because more repeated sequences reduces the value of variable-length encoding). But more than that, what bothers me is that there's this false truth that server-side rendering is a requirement for modern architectures, which must result in hundreds of thousands of wasted engineering hours trying to enable the idea of server-side and client-side rendering with the same code.
This is not about time-to-first-byte either. Yes, the user-perceived latency matters, but the idea that server rendering even solves this problem is again utterly false. Sure, the time to very first byte ever may be faster, but that's not a winning long-term strategy unless you never expect your client to request the same content twice (or come back to your site at all). When properly cached and synchronized, the client-side-only app has many orders of magnitude faster TTFB, because it's coming from disk or even memory, and can be shown immediately. The only thing left to do is ask the server "what's new since my last timestamp?"
All of these benefits seem to be completely disregarded 99% of the time because the golden "SEO" handcuffs are already on. I really hope we can get away from this mindset as a community and rather let the better-engineered and sites with the best and fastest UX over time will start driving search engine technology, instead of the other way around.