Even then, it's not what's important. The core important thing in the product is that it does a job the customer needs done. If you write a program that provides complete feature parity with the incumbent with better engineering principles, you're going to lose because the engineering principles aren't the job the customer needs done.
Where it will make the difference is that your company will be able to respond to changing requirements better than the incumbent.
So solid software engineering is never the product for the customer. It might be the product for the company, depending if the company actually needs the improved developer efficiency and happiness it provides.