People really seem to believe that code is the only thing you need to make a SaaS company. It's like thinking a line cook is all you need to open a restaurant. There are so, so many other components to running a business.

I agree!

Although the proponents of this idea argue that companies will create and (!) maintain many tools in-house.

It’s not so much about running a business, since you don’t sell anything and only have internal customers.

SaaS is mostly sales.