usability of --skip-tags is worse than skip_install

[fsperling]

Hello,

in a recent version the skip_install variable got deprecated in favor of using --skip-tags.
I couldn't find any explanation why this was done, I'm guessing it makes the code easier.

I found that for my usecase --skip-tags doesn't work.
I have a playbook which uses the prometheus role. The only way I found to skip the installation is during the invokation of ansible-playbook.

ansible-playbook my-playbook --skip-tags prometheus_install

It doesn't seem possible to set it in the playbook.
Thus the user always needs to remember that the playbook needs to be run with this extra option and has to type it as well. In my view this makes the usability much worse.