Although the legacy SDK distribution has been stopped, many people still keep it.
Many people destroyed their VCC projects by importing the legacy SDK, based on their old knowledge from the legacy SDK.
(There are also several outdated articles that guide users to override import the SDK when trouble occurs, and the same is true for those who refer to those articles.)
To avoid such trouble, please prevent importing legacy unitypackage SDK in VCC/VPM SDK.
It may not be perfect, but it should be helpful.
As examples, lilToon and UnlitWF have a mechanism to prevent importing the unitypackage version if it has already been imported by UPM or VPM.
(Both are licensed under the MIT license.)