You incorrectly assume that all power users wish to modify their operating system and hardware, and in doing so exclude professionals who prefer to use the tool as it was sold to them. There are many reasons why professionals with the capability to modify software and hardware behaviors might choose not to; conflating “power users” and “professionals” disregards that distinction, and by doing so ignores why Macs are successful among those professionals who are not, as you label it, “power users”.
I said nothing about modifying anything, if anybody is assuming things, it is you.
Case in point: my 70 year old aunt and 8 year old neighbour can change the RAM and storage on their computers, that doesn't make them power users.
An Academy-winning Hollywood director I know bought his Windows-based computer pre-made, doesn't modify anything on it, just uses Da Vinci Resolve, but requires the absolute pinnacle of performance. He's a power user.
You’re absolutely right: the term “power user” isn’t well-defined enough for us to use in this discussion without considering what it means. What definition are you using in your comment above? I don’t have any strong preference, and will accede to yours.
The typical one of having advanced skills and advanced needs. The thing that Macs did used to cater for.
Software-wise, now both Logic and Final Cut are a bad joke, especially by modern standards. That's just one of dozens upon dozens of reasons why Apple aren't the go-to anymore.