Huge disagree on this. Old code tend to be much more terrible because the tools were terrible. They gave little incentive and absolutely no help to write even passable code. We end up with a mess of poorly documented, sparingly commented spaghetti code that sometimes work, often by accident.

Nowadays, we have linters to point out common classes of mistakes, programming languages with actual type systems to enforce invariants, integrated testing tools, etc...

Note that, yes, we do still have new, terrible codebases. But at least the tooling nowadays raised the bar to have a minimum floor of quality that, while very low, is still oh so much higher than it used to be.