The deprecation warning is just saying that the old names aren’t going to be supported forever. If you explicitly declare that you need 8.2+ (or something), it suppresses those as well since you need to use the old names to support the version you’re stating. If you say find_package(VTK 9.0), support for the old names is removed since you are saying you require 9.0 anyways (use of VTK_USE_FILE is also a hard error in this case).
I would recommend using the old names and declaring your minimum version (probably 8.0?). That will allow you to use the old names without warnings or any other complicated queries.