Crucially, the USPTO disagrees with you (although, who knows? That could change in the future). Is the company providing a canvas, or a collaboration tool that
uses an abstraction of a canvas to operate? I think that you're conflating what a thing is with how that thing is constructed. It
is a collaboration tool. It
uses a canvas. "Canvas" isn't a generic word within the realm of SaaS collaboration tools, so a trademark on that name, in that context, should be valid.
In your example, a chainsaw company could produce a product called Chainsaw, but it couldn't (shouldn't be able to, at least) gain a trademark for that name.