But what if Adobe actually had (and maybe still are) tried to make Flash performant on non-Windows platforms, but can't because the codebase is such a mess? In

But what if Adobe actually had (and maybe still are) tried to make Flash performant on non-Windows platforms, but can't because the codebase is such a mess? In that case, yes – Flash did fail because of a bad codebase. Then again, Flash is probably an extreme example, but it just goes to show that there is a point at which a bad codebase will interfere with your product.