In 1812，the year Charles Dickens was born, there were 66 novels published in Britain. People had been writing novels for a century—most experts date the first novel to Robinson Crusoe in 1719—but nobody wanted to do it professionally. The steam-powered printing press was still in its early stages；the literacy rate in England was under 50％. Many works of fiction appeared without the names of the authors, often with something like “By a lady.” Novels, for the most part, were looked upon as silly, immoral or just plain bad.

上面一段摘自2020年高考英语浙江卷阅读A。

请问 just plain bad 的语法对吗？用形容词 plain 修饰形容词 bad？