These kinds of write-ups are so key to driving adoption of a new technology. I'm still not super interested in HTMX but this write-up has done a lot of the work already toward nudging me that way. Well done!
Yes, as I remember it it was a 'back to simplicity' of the early web idea. Rediscover the power of hypermedia. I don't know HTMX well, but am following Datastar [0] which was inspired by it, and their selling points are Simplicity and Performance and take it some steps further than HTMX. The approach does shift logic / complexity towards the backend though.
In general, I agree because it's easier to test and monitor back end code. However, if the complexity also comes along with heavy CPU load, I like to push that out to the client.
Except you have no guarantees what client side compute is available. Sounds like a fools errand if you are looking for consistent performance.