Well, you say that but in ET you could complete secondary missions that gave you access to the last stage before the primary 1st objective had been completed. This wasn’t a problem, it made the maps vastly more interesting, defences had to be more alert and proactive rather than what you had in Brink camping behind boxes and behind railing on balconies (generalising yeah).
I’m not sure the occasional newbie going the wrong way warrants simplifying maps into the linear bore fest that we were treated to in Brink. A well designed map will make sure you go the right using visual cues plus you can add objective markers like ET:QW, though sometimes there’s no helping some folk but still lets not restrict our possibilities over something like this. On some maps in the past the previous stage have indeed actually been used to take run a document objective through and back to your current spawn in order to be safe, takes longer though, much longer. Remember these maps aren’t as straight forward as Brink:
Link here: http://pastebin.com/RPG91NUh because pasting onto here even with code tags messed it up. Should have drawn picture instead ha, grossly simplified but hopefully you get the idea. Also remember you can select where you spawn in previous games, something Brink was lacking due to it been designed out.
Not all maps were like this and some maps that did let you get to last stage, like ones in ET:QW, there was a delay from when that last objective was doable from completing the previous objective.