Technical debt is the accumulated cost of quick, makeshift or under-thought decisions in code, a data model or a process. Like financial debt, you can "borrow" speed now in exchange for more expensive, slower changes later - the problem starts when a company stops paying it down and the debt keeps growing.
With generated or hastily written apps, technical debt typically shows up like this: nobody on the team knows exactly how parts of the system work; a small change (a new tax rate, a new field) requires a disproportionately long intervention; and once the one person who understood the code leaves, the system effectively stops being maintainable.
No-code platforms don't erase technical debt entirely, but they change its nature - the logic stays readable in the building blocks (databases, automations, views), so another person on the team can pick it up, not just whoever wrote the original code.
Related: AI will write your app. But who's going to fix it a year from now?, Automation without the black box.