"uuuuh, so don't use it, duuuuu..."
Its so cute when you are trying to dementate something ...
As when kids thinks that two inifinites is twice as much as infinite.

Its a problem when a game is designed/built around fast travel.
I wonder what that even mean.
Could you elaborate?
Or is that just some vague catchword you are hiding behind? :P
remove fast travel outside of not being at portal, remove send to camp feature, and link portals to specific other locations, not having them all linked together.
This all can be done while not ruining other people game ...
If you dont want to ... just dont.

Seems simple enough ...
What is the problem? Why do you require other people you never seen or met to play their own completely separated SINGLE PLAYER game that dont affect you in any way ... the way you want it?
Where is origin of this urge to adjust everything on system level so you can get what you want but are too ... dunno unwilling, lazy, incapable (fell free to pick) ... to get it youreself?
Now when i think about it ... i think i know ONE possibke reason that would explain such behaviour ... but i still find it inprobable that so many people on this forum would share the same diagnosis. O_o