Take decisions :). Customization as a way to make an app better for my personal needs versus me (as a designer) not knowing how the app should be used and shifting the responsibility to the end user.

When a tool I use across jobs has a bunch of features that are controlled by toggles, then what I get from the tool changes every time I change jobs. No two teams are going to vote 'yes' on the exact same set of features, which means each job is a new adventure in 'will I be able to make this tool sit up and bark for us or will it be a constant source of stress?'.

Making UI elements like the month picker optional screams of internal schizophrenia in the team. Just turn it on. If you have some loud customer who insists they not be there, make a custom CSS file that hides them.

Don't make your users have to spend scarce social capital to get features that were available in the box. Just turn it on, man.