Except for some limited examples of features which are opt-in or allow being disabled, no, there isn't any kind of general granular control for "please just take these features away from the main site pages" available in the phpBB ACP.
What it sounds like you're looking for is a custom style for your site. Since at the style level the style can choose to "ignore" and not present features that are otherwise standard on most phpBB sites, regardless of the fact that phpBB itself still supports those features.
This simplified style could be the default for the site and all new and existing users. But this wouldn't prevent you or other users who did want access to more features from being able to choose a different style when desired or necessary, which did present more of the phpBB standard functionality.
There isn't an existing style which comes to mind that intended to simplify and provide only limited functionality. There are many styles available of course, but they understandably all tend to default to "offer all the features that phpBB supports." Maybe someone else will have a suggestion in mind of an existing style you could look at.
But since your preference of "what doesn't seem necessary for my users" could be unique to you and your site, it seems more likely that you might need to commission (pay) for a custom style created specifically for you, by
posting in the Wanted! forum.
If you end up posting for work to be done in the
Wanted! forum, recommend that you have a very specific idea of all the things you would want removed. For example, including screen shots of your existing site pages, with all the items you intend to remove circled.