What would make it great in your eyes?

Not OP, but I use canvas all the time (Thank you!) in preference to something like Miro because I really value the open format and being able to keep the file. Something that really holds me back is the inability to use different shapes for the nodes - a use case for me is creating flow charts and process diagrams, so being unable to use the standard shapes for those is a challenge.

Still the best option though!