I'm a huge fan of the concept of tech debt. In my pitiful layman's terms, tech debt is the debt burden that exists in software, infrastructure, etc that is the result of decisions made in early versions of the product that made sense then, but don't scale.
Perhaps the backend database started as a simple flat file, but as time evolves that doesn't scale to meet the needs of your users.
Perhaps you hard coded in language on images for navigation or images, which makes it painful to translate into other languages.
The idea of tech debt can be applied to other areas as well. The Chinese written language is a great example - by having a single written language standardized regardless of local dialect, China became culturally coherent across a diverse group of peoples and geography.
But that pictographic language doesn't scale well. The burden of language literacy was reasonable when a small percentage of the population were poets, scribes, state bureaucrats. But when you're trying to bring literacy to a billion people, or even have people from other cultures learn your language, it's a significant tech debt.
Internal combustion engines. Coal powered energy grids. Distributed energy grids in a world of regular Class 5 hurricanes. A carbon intensive industry. Elements of our current democracies also have significant scaling issues and make assumptions around citizen involvement that were true in the past but are no longer.
Tech debt is all around us, and it takes real will and effort to break the old models, shed the legacy and build new solutions.