In a mountain of tech debt, the main anti-pattern is stopping all value-add work while you deal with the debt, at least if you want to gain/retain customers. When I was in that situation, I set up a "debt" Kanban board and allocated a fixed amount of time (20%—one day a week?) to that board, spending the rest of the time adding value. Of course, continuous refactoring is also part of the add-value process, so it's not purely binary.

Source: x.com/allenholub/status/1827396707895947759