It’ll train everyone to ignore the warnings, so if a different platform implements such a system more sensibly users will be inclined to ignore those warnings too now. Overusing a warning is a really quick way to make people ignore it even where used correctly.
If you placed wet floor signs everywhere just in case, fall injuries would increase.

Systems around this will develop, either people will learn to dig up the dms, or it’ll be incorporated into normal communication. It’s already become the norm to use friend requests as a dm request on discord, due to previous dm restrictions.