4e was definitely far more collaborative because of the roles, power options, etc. You could build it into your character as much or as little as you wanted.
4e does bring up the biggest issue lying at the bottom of this pool of water. It was considered an unpopular edition because it made some drastic changes that didn’t feel like D&D or tried too hard to make an MMO, however you wish to look at it. The changes were too much from some of its original mechanical principles. In that way, it may be impossible to successfully incorporate these kinds of changes to D&D because, when it comes down to it, the audience determines if it’s a good Edition based on its familiarity to previous ones while changing just enough to make it unique and yet similar.
3e was able to do it when they converted D&D from THAC0 to d20+skill rolls. But they had to keep other things very close to home, hence why we have Difficulty Class to work with Armor Class because that name change alone could have been too much of a change. It’s a very delicate balancing act.
So back to the initial conversation…
Do you think you could take your character and do just as well alone if the dungeon was custom made for only one PC? Or would you be weaker because you depend on your allies to do as good as you do?
I bring all this up because I’m fascinated with the application and interpretation of mechanics, which is not always the same. It’s like how we all missed that Monopoly was designed as a game to warn us about capitalism but was packaged to embrace it. Hence my theory that D&D isn’t built to encourage collaborative actions but it’s played this way.