Is your company's core product a billing system? Then it pays to innovate on billing systems and differentiate from competitors.
Do you just need a billing system so you can collect money and move on with innovating where it actually matters? then buy and don't make.
wasting time on doing novel things that don't differentiate your business only puts you behind your competitors.
I wish this was more common but every time I had a manager without an engineering background or one who was a weak engineer, the ride was not smooth to put it kindly.
They don't need to be software engineers but they should have an overview of the industry.
My experience has been that those who are too precious about the only role they've ever had (an "engineer") are difficult to manage precisely because of their inflexibility and lack of curiosity. It's ironic isn't it?