This isn't (or doesn't have to be) about laws specifying how
all software has to be made.
What they need to specify is the standards for software that certain types of organizations can use. Like government agencies, government contractors, medical organizations, construction and engineering firms, and probably some other kinds of large private businesses, depending on their industry.
Basically, if the software your organization uses can cause the level of destruction that Horizon did, it needs to have specific certifications, or you can't use it.
In order for such software to be certified, it needs to meet certain clearly-defined standards of quality, potentially including having all the technical leads of some level (or just all the developers, depending on various factors) be licensed, and have their licenses on the line of something like this scandal occurs.
It's not a panacea, and it would definitely be an absolute bear to get the terms of all of it defined both clearly and in a way that is likely to actually produce a quality product, but IMO it is likely to be worth it in the long haul.