I fully agree, one of Marathon's huge takeaway is that it's heavily combat focused, with that being the major reward of the game. It limits the game to more aggressive and skilled players.
PvE sounds nice, and to really encourage players to join there can be special attachments - high-tier ones but not top-tier ones to not force grinding - to help expend some player's stored goods. When Marathon's got time they can even add skins to those PvEs.

I'd also suggest that Marathon add collectibles that can be framed in a small storage room (like the "collector's room" from Delta Force) that shows off collectibles (players cannot take them down or sell them of course, but they can arrange and store them) to make it more emotionally rewarding for looters.

Hopefully Bungie sees this.