(LO-Dev here)
It is one of those "death by a thousand cuts" situations. We have fixed a ton of issues, but there are still a ton more.
Sometimes the formatting changes between versions of Word.
Sometimes the formatting is off because we have bugs. Sometimes Word has a bug, and then we have to figure out what that bug is and try and have the "same" bug.
Although it is a valid point, you are missing that it's Microsoft who prevents everyone from doing it [0].