For running in Plack-mode, people needs to:
sudo koha-plack --enable <instance>
sudo koha-plack --start <instance>
sudo systemctl restart apache2
after creating the <instance>.
What I meant is that we should have people avoid the need for those commands. And people with specific needs that require non-Plack setups can do it.
I started thinking of this in the context of bug 20134 [1] BUT also in the context of bugs 18315 [2] and 7174 [3].
Both of the latter bugs propose interesting ways of refactoring authentication, and I'm sure abandoning CGI-mode could help simplify the process.