I don’t think the underlying point is true: big companies don’t necessarily write bad code.
A big company is like a collection of small companies. Code quality varies depending on where you are in it.
Similarly, nothing leads me to believe small companies are any better. Some are excellent. Some are nightmare spaghetti.
Big companies oftentimes have cultures and leadership that lead to bad code.
Big companies are insanely slower due to beauracracy and rules, even if talent is identical. I have seen it happen so many times as companies grow and go IPO.