At work, when I do internal tools, they are usually well received. They also pass just below the threshold of having their looks be judged. They're not ugly, because they're almost not there.
Very plain HTML: HEAD+TITLE, H1, H2, UL, OL, A, IMG, INPUT, BR, TABLE, P Javascript as needed, usually embedded in the HEAD There is no CSS.
There's simply no design to attack, no colors or alignments to disagree with. It exposes the interface to communicate with the backend, nothing more.
It's also the fastest and simplest way of getting stuff done, if you don't need to expose it to "end users".