How do you convince your team to pause feature development to fix tech debt?

Early on, moving fast and breaking things was essential to hit our launch dates. We shipped fast, but we built up considerable technical and design debt along the way.

Now, every new feature takes twice as long to build, and minor bugs are starting to creep into production. However, taking a full sprint just to refactor code and clean up UI debt risky when users are constantly asking for new roadmap items.

How do you strike the right balance between maintaining shipping velocity and taking time to refactor foundation work?