The creator of Excalidraw made a comment somewhere else on this page about how well Excalidraw+ is doing.
> The plus plan has been very successful from my point of view, we’ve been able to bootstrap the business and make our first hire. The key realization is that while the unauthenticated open source model works really well for individuals, it’s hard for companies to adopt.
> They want authentication, security policies, private spaces to collaborate, access control, search… all of this requires having a company behind it in practice and the open source model doesn’t work as well.
> The two versions so far work really well alongside each other right now.
I think there are certainly products out there that can't pull this off. And, that's a fair point.