I agree that Canva, Miro, draw.io, Freeform and many others set the bar for whiteboard apps. But: Is Obsidian Canvas a whiteboard app? Should it be a whiteboard app?
Personally I’ve changed my mind since my initial experiments with Canvas.
At first I was comparing Canvas to mindmapping tools like Mindnode. I ran into the same limitations as you did and I was very disappointed.
Then I saw Canvases showcased on Obsidian’s Discord server and in some Youtube videos. And I discovered the website https://infinitecanvas.tools/ which shows images of mood boards and of book pages laid out on the floor. These images made sense.
Now I think of Canvas like a pinboard or like a layout table for existing notes.
With this expection in mind, Canvas turned out to be surprisingly useful.