It's seems like at some point around five years ago the three tier architecture with it's division of labor vanished over night. I'm not saying things were perfect back then but I've never seen any demonstrably objective reasons why it was replaced.
I went from having to be mindful a few configuration items which arose from deploying my war to different environments to slogging through configuration hell in the Terraform and AWS world. I've been learning way more about Ops than I ever cared to know while at the same time becoming a -10x developer in terms of shipping business value.
Yeah, duh. I render simple HTML templates on the server and serve them as browsers expect them; not with a thousand lines of JS for topping.
I'm reminded of a post from a few years ago where someone's website had a table of items with [delete] links and would take database actions based on GET requests to those URLs. Who cares? It looks the same to a human browsing it.
And then it got crawled by a search engine which followed all the links to see where they went.
But if you're not doing anything unusual like that, I don't see how prefetching HTML would cause any problems.
Top be fair it has reduced our server costs a bit (after maybe 6 months of developer time). I am unconvinced it will be worth the hassle.
Are the improvements worth $125,000?
Though one comment I saw about Kubernetes on here a few weeks back concerned an old schooler like me. The guy suggested that if something goes wrong, just kill the pod and let kubernetes bring up another. Apparently that's the way you are supposed to do things. Something seems really wrong with that approach to me. Just throw resources at the problem with very little understanding of why things went wrong.
Tbh, I have no real world experience in this, so it might just be my own delusion. However, I've recently started getting into self-hosting some of the services I use. I'm using a simpler infrastructure than what OP described and while it is the right choice for me and a useful skill to have, I feel like it absolutely won't get me anything in the sysadmin/ops/etc. job space. I've actually considered adding more "enterprisey" tech to it (like Ansible or comparable stuff) just to make it more sexy for recruiters.
Your resume needs to have lots of fashionable buzzwords rather than pragmatic good enough / keep it simple choices. You must keep on learning (lots of things rather than mastering any one thing). I can write a really nice site in standard Django with some JQuery, and it will take me half the time that adding React to it will. But adding React will make me much more employable and get me a better wage.