Incremental vs incomplete

Incremental improvements are changes that better a system over time without ever taking away its ability to stand on its own; if the project where those changes come from stops today, everything will be fine.

Changes that break the system for anyone who interacts with it are incomplete changes; if the project where those changes come from stops today, it's not going to be okay.

Incomplete changes are not incremental changes, and there is never a good time to ship incomplete changes.