It totally depends on what you want to succeed. In our case, for example, we break our python code into microservices so it is more important documenting the APIs rather the code itself. If you are building complicated libraries, yes sphinx is the choice to go. Most important of all is to understand your deployments and your code lifecycle.
I could not disagree more. SW is great for several stuff. For example business logic, API creation and consumption and stuff like that. SEO is only a minor benefit from switching to that technology. I would totally recommend to follow the work on json-ld and schema.org and you will see that it is not what you have heard.
I would only agree that SW is still a difficult concept to understand and start using for any developer and needs more effort on that direction.