I appreciate your thoughtful questions. Replying has led me to think through the problem more thoroughly.
Before this discussion of DW was split off, the topic was “Sequoia issue with USB hub: “allow accessories to connect” missing”. Various posts confirmed that macOS Sequoia had problems, ongoing and recurring, with drives connected by USB. Anecdotally, such issues seem fairly widespread, but maybe not persistent. However prevalent, that is what the original thread was about. We can all hope that whenever malfunctions appear in macOS, Apple will immediately correct them, making third party repair applications irrelevant. Good luck with that. I’ll go you one better. My hope is that as Apple continues enhancing macOS the code will be tested sufficiently that essentially no new bugs are revealed on final release. A nice idea but not very likely.
Even if our wishes for a bug-free macOS did come true, there still might be a market for third party tools.
I don’t have the reference handy, but recently I read a review comparing HFS+ and APFS for various kinds of uses. Each had certain advantages and disadvantages, but if I recall correctly (and I read correctly in the first place), both accumulated problems that were not easy remediable, which detracted more and more from function. If I am remembering this correctly, a full recreation by DW of the logical representation of the disk might be useful after things bogged down. (I know this paragraph is way too sketchy, but maybe someone reading can supply the reference, or other relevant information.)