What worked for me in the past is being upfront and honest about it. You don't know you're walking into a dead-end job so it's not your fault if you got stuck. What's important is: what did you do to try to make it better? What did you achieve with that effort? If not much, what did you learn?

Maybe your next job after the dead-end one won't be a dream design job but it should be a significant improvement. That way, the one after that might actually be your dream job. You need to think long term and see jobs that aren't ideal as transitional.