Before I start, I won't address the issue of whether or not your boss is right to insist on classic ASP. You haven't given us enough information. If you have a very large body of existing code in Classic ASP that is 95% good enough, and you are doing small maintenance tasks, then it's probably a good idea just to stick with Classic ASP... the cost of porting everything to a new language might be too high. However if your boss is launching new projects in Classic ASP, well, there's no excuse for that. And there's a whole range in the middle. So I don't have enough information to weigh in on that, and won't bother.
But I do want to address your precise question... how to make coding Interesting.
Is interesting a good thing in coding? Remember the Chinese curse, "May you live in interesting times?" Well, it's probably not Chinese... but the thing is, I question whether all forms of programming should be interesting. Sometimes you just want it to be easy and straightforward. The biggest code messes I've ever had to clean up have been caused by developers who are tired of the simple straightforward way of doing something and need to find a clever language feature that nobody has ever heard, just to keep their own mind stimulated. I remember finding 20 lines of C++ code whose purpose I just could not decipher. It turns out to have been some kind of subtle trick by a developer to insure that certain variables were initialized to 1 if you forgot to initialize them. It was ridiculous, and boy was it interesting. But it wasted everyone's time--his included.
There is a lot of virtue to writing most of your daily code in a "boring" language. It means that you can use your brain to think about the application domain instead of trying to work out why the latest language feature you just came up with isn't working the way you expected it to. You can usually work a lot faster if you understand your language and its libraries completely. And that means you can use your brain cycles for something like thinking about making your application more interesting, more useful, more profitable, or more usable.
To keep your mind sharp, use your spare time to learn interesting new languages. Work on open source projects or work on your own projects.
Remember, I am not defending the use of Classic ASP, and I'm not saying it's a good idea to use it because it's "boring." If you think it's a virtue to use an "interesting" development environment, more power to you... but you're focusing on the wrong thing. A good sculptor doesn't want an interesting chisel... that would get in the way of making nice statues. A good painter isn't looking for "interesting" paintbrushes. They might fool around with interesting tools, but they're going to do their best work with the most boring tools possible--the tools that are so boring they disappear and let the artist work on the art.