As anything it is just a tool in our toolbelt and should be used carefully. If our system contains same user validation in 2 places, changing it in 1 place may lead to issues, which are difficult to discover. However forcefully implementing DRY everywhere can lead to coupling and lack of separation between modules and influence deployments, and work of different teams. Its more difficult to build context of the implementation, if one needs to jump from file to file. There’s a balance to when to use it or not.