My strong assumption is that the majority of times that people toggle off Wi-Fi, is to temporarily resolve connection issues. Keeping it off permanently is probably not what they want. The UI warns you of the temporary nature too.

Those who don’t use it, like you, quickly discover the actual way of disabling it. It’s good UX design that aligns with most user’s preferences.

The warning in the UI was tacked on only after people discovered and started complaining about this initially-hidden change.

The change removed functionality that was previously available: quick access to the real on/off toggles for these functions. There's a page in Settings devoted to "Control Center." I would have no problem with it if there were a temporary/permanent option there for these toggles, even if Apple defaulted them to the current (temporary) behavior. Then everyone's preference would be served.

A lot of people use bluetooth devices - watches, headphones, car, speakers, etc. It makes much more sense for the toggle to only temporarily turn off bluetooth because in today's majority use case, that's what people are likely wanting.

It sucks that you have to deal with it for your minority case, but that's just the way things are. There are work-arounds, but you clearly don't want to try any of those. You're prerogative.

And Wi-Fi is more efficient than cellular. It's best to use that as much as possible.