There is an abundance of mediocre and even awful code in products that are not failing because of it.
The worst thing about poorly designed software architecture is that it tends to freeze and accumulate more and more technical debt. This is not always a competitive issue, and with enough money you can maintain pretty much any codebases.
When you work with F500s you end up seeing code and culture that is absolute balls and that I would never work directly for all the time. And yet roles are always filled. And when the economy gets bad, they have decent engineers.
I call it the fast food quality theory of economics. When the economy is good, low pay jobs tend to have low quality employees and it shows in their products. When the economy gets bad higher quality employees end up downgrading because of layoffs and the quality of these low tier jobs improves.