The history is full of distros going out of business due to lack of fund. Think what happened to Mandriva for example. And Canonical is currently working on cost cutting initiative like "switching UDS to virtual event". They are also not planning on Mark money, or they would not have implemented stuff like "amazon referal", or tried to sell music. In fact, if Canonical didn't care about the money, they would have done a fundation like Mozilla or Wikimedia.
So yes, sustainability is what matter, and Canonical is nowhere being sustainable for now.