Am I the only person for whom this looks like horrible, over-complex, write-only spaghetti code?
Sure, you likely wouldn't want to maintain a more complex project with this stack, but IMO it's perfectly suited for an RSS reader. To me this is a prime example of solid full-stack web development, and I applaud the effort. Kudos to the author for choosing the right technologies to balance the features/simplicity, and integrating them so well.
What do you think about: https://htmx.org/essays/locality-of-behaviour/
I say "on the whole" because there are always counterexamples to any maxim. The article realises this and mentions 2: DRY and SoC.
Writing good software is often a matter of taste.