The answer is likely depends on the community and what usage patterns you expect. If you feel you like you’re able to safely experiment, you can try different things and open up a channel with your users to share their feedback (e.g. a topic in Contribute > Site feedback). Make a change, ask for feedback, iterate.
It sounds like all they want is the main section?
Do others who use the site have opinions? Maybe it’s worth reaching out to a few people to ask them whether they currently use any of those sections?
If it’s just one person who feels things are more cluttered than necessary, perhaps they want to collapse the sidebar completely most of the time, which they can do by clicking the hamburger icon in the upper left. If everyone feels the same way, perhaps it does make sense to hide those other sections in some fashion.
There is also the option to set the navigation menu site setting to header dropdown instead of sidebar, that may be worth trying out.