During a sprint planning, the development lead highlights the importance of working on technical debt...

In Agile, the Product Owner is responsible for prioritizing the product backlog, which includes both features and technical work (such as reducing technical debt). If the technical debt is critical for performance, it must be addressed even at the expense of delivering new features. Once the team and Product Owner agree, these tasks should be pulled into the sprint backlog during sprint planning.

Per the Agile Practice Guide, “The product backlog may include technical work, bug fixes, and other items necessary for product health—not just features.” Adding technical debt items to the sprint backlog is an accepted and necessary practice for long-term product sustainability.