I was a very junior dev when I worked for a huge health insurance company, I was placed under a senior dev to learn JSP and Java Servlets using an internal app. I quickly ran through a book on JSP to prepare for the project.
When I get there, the guy had already written one page of the app, and he did it by doing System.out.println in the servlet for ALL THE HTML. In other words, he didn't use JSP templates at all.
System.out.println("<html>");
System.out.println("<head>");
System.out.println("<title>This janky ass code</title>");
I looked at that abomination and said, "This isn't JSP at all...." He rambled on about sometimes in a project, we just need to get things done with the tools we knew, etc. etc.
I went to our boss and told him I wasn't learning JSP, which was the mandate of the company back then. He just kind of smirked and said, "Yeah, that sounds like Ken. He knows programming, though, blah blah blah."
2nd worse boss I ever had, the dev was a lunatic, and that company was a joke.