That's the main problem beside of the fact that there are/were serious bugs. In general I can feel you. I had the same issues and questions two years ago. I decided to code my own ERP and changing ASM to our needs. It works great now. But obviously most merchant can't do it and it shouldn't need to do.
Actually my main hope to the new owners is, that we get a place to discuss and vote for such bigger projects. No dev can ever build a working ASM without clear requirements. I also had to spend dozens of discussing hours, to understand how things really should work (for us). A dev doesn't automatically consider it a problem, that you can't search fast for the stock quantity as they never did inventory. They may also think, that it's enough to have one location per product. But some merchants (as us) need multiple locations for the same product. The list goes on and on. But only a discussion with a dozen of serious merchant, will show what is important in general and what is more like a specific business usage.
Btw such attempts can fail easily as my own example shows:
This is true and the main point, why we started to use ASM. But I believe it's not entirely correct. As far as I remember the "usable_quantity" has more an interpretation like: do we have broken items in storage? It's not totally nonsense, but we don't use it too. To exaggerate a bit: ASM was designed as it will become the most powerful erp ever, but was only finished 10%. There are tries to calculate product costs over multiple suppliers, currencies and stuff. 🤔