Sometimes support in IT means supporting the app. There is good and bad about this. If the app is not widely use, that means it may be harder for you to bring this knowledge forward to other opportunities and companies.

But having said that, the most important is how you apply yourself, i.e do you know what this system is about, how do you support it, how do you interact with your customer (either internal/external), how you deal with challenging issues), how do you work with your team members, how do you try to improve the knowledge base / process, etc, etc.

Of course, you may opt to support more versatile elements like Linux, Java app, etc.