TIL: NuGet supports new csproj not PackageReference
In a project with the new csproj format and dependencies described with PackageReference, if you want your dependencies properly included in your package use dotnet pack instead.
If you are stuck with NuGet, you will have to create a .nuspec file and precise <dependencies> and <frameworkAssemblies>.
TIPS : you can use dotnet pack to generate a well designed package and then open it with NuGet Package Explorer
to retrieve its metadata for your .nuspec. For <version> use $version$ if you want your CI/CD to handle it for you.