There is also #8988 (closed) about custom fields. It there is some flexible architecture like in Drupal - all entities can have custom fields (and some form widget and some formatter), so building other features what needs to store data is more simple.

It's not customizable enough and there aren't enough distinct fields for inevitably complex work tasks. Google Sheets fixes that. No, it's not a to do list app, but that's why I love it. It's an app I already use. It's extremely customizable.