Create a default view for all users and devices

For managed users your control goes to the level of you defining some restrictions (e.g. regarding the age ratings they can access) and you can define what online media sources they have access to.
Beyond that they’re free to customize their own home screens or which libraries they want to see pinned.

For un-managed users it’s completely up to them.

I’m not saying I don’t see where you’re coming from.
My takeaway from those discussions is that people have a different take on how they consider they want to share their media… some want to take 100% control on every aspect how those users watch their media (preferably even if those friends have a server of their own and might have ideas/preferences of their own)… while others consider how to lower the threshold for their friends to enjoy Plex. Usually the underlying idea is the same… but the resulting expectations differ.

Personally I prefer enabling the family members with whom I share my videos so they can use Plex to the best of their capabilities. For most of them, sharing the “how to navigate/customize Plex on mobile/big screen apps” support articles did the job.
Admittedly I’m not constantly adding new libraries but have a relatively stable structure within my Server.

I also liked the discussion we recently had with a different user who looked for some kind of “introduction” to support any new users from how to deal with that invite and some house-rules for his/her server (e.g. please don’t transcode media unless it’s necessary)…

Edit: added link to the “new user/share introduction” thread