I don’t agree. Hover Editor works in a separate window, and is barely more convenient than clicking through to the transcluded file. And Make.md radically changes the UX, so it’s not a solution if all you want is in-place editing of transclusions. But it does show that it’s possible to implement.
A recent post on the Obsidian subreddit asked users what missing feature they wanted most, and in-place editing of transclusions came in a close second, so obviously a lot of people want it. And if you used transclusions a lot and had ever experienced it in an app that had the feature, you’d know why.