Tech debt is most easily measurable in repetitive operational work. Measure it. Bring a story to your leaders: "We are spending 60 hours per week doing repetitive task X. With 200 hours of work, we could eliminate this work. It would pay for itself in a month."
If your leadership declines to take you up on this, escalate. If that fails, you must choose between continuing to do the repetitive operational work as instructed or leaving.
If your leadership declines to take you up on this, escalate. If that fails, you must choose between continuing to do the repetitive operational work as instructed or leaving.