Bad code exists everywhere. You shouldn't defend it, even if it is your own code.
Bad code isn't bad on purpose. It sadly happens. But because it is bad, you shouldn't defend it.
For example, an application does whatever you need. But it crashes from time to time. Software shouldn't crash and you shouldn't defend it just because it does whatever you need.
Your internal application works on a single browser. That's bad. "But maybe the other devs thought it wouldn't be worth working on all browsers". No. It is bad. You shouldn't defend the other devs because they decided to focus on a single browser due whatever problems they were facing. Sure it wasn't nice that they had to do this trade-off, but it is still bad software.
If we keep defending this kind of software, we will still get bad software.