I believe you are looking for Minimum Lovable Product (MLP). Unless you are serving a very niche market where existing options are total crap, nowadays users can find direct/indirect alternatives easily, making the “viable” threshold so much higher.

Also, UXUI could play a larger part of the “viability” if you your target audience are more towards designers isn’t it?

Looks interesting! Is there a way to create a step without questions? For example, if someone want to have certain steps to be a “reading” instead of a quiz?