If you're able ti dismount you can loot boxes and access things like a normal human being. In order to build things all you need to do is either be in a drop and a person put them in your dinos inventory, or you dismount and pick up dropped items to build with. You can even use Structures+ Blueprint Converter to convert items to blueprints so you can craft your own stuff.

But it's all dependent on if you can dismount in the first place or have tribe members.

It doesn't seem like I can... so I guess I can't. ACM allows me to build structures as a dino, but as for interacting with Loot boxes and obelisks, looks like I'm out of luck.

So much for a spry and limber raptor going toe-to-toe with a boss, ey? Unless I got someone else to open the gate for me.