You (understandably) skipped over the point he was trying to make:
In System Shock 2 there was no need to lock anything behind you. The world you were in was built small enough and diverse enough that it remained in your mind as you traversed it. You weren't just going through anonymous tunnels, but exploring a space ship where you always had at least a rough idea of where you were.
Mass Effect 3 has a gigantic world, and has you enter, again and again, dungeons that simply start out as holes in the ground with little guidance for the player as to how they're structured, built with repetitive (though high-detail) 3d assets and textures, thus making it necessary to lock things behind you, since there cannot be a reasonable expectation for the player to keep their bearings.
Every bad experience with navigating a level is because of shitty level design. Every bad experience with "I don't have enough health, I don't have enough ammo" is because of shitty level design.
Go back and play Blood, or Duke Nukem, or Doom, and pay careful attention to the way that the levels are made. It's vastly, vastly different than the funhouse rides created for modern shooters.
Duke Nukem? Doom? If your standard for good level design is Duke Nukem, then the conversation is over, with the conclusion that we have different quality standards.
I played Duke Nukem as a teen, with truckloads of time on my hands. While fun, the game requires teen-levels of free time to get unstuck here and there. Nowadays I would definitely not spend the time I did.
Make a level big enough and people will get lost. Different people will get lost in different points. So, the solution is to either make smaller levels or to lock out areas. Even Fallout, a master piece for these games, closes out areas in critical puzzle points so it can reduce search space.
In System Shock 2 there was no need to lock anything behind you. The world you were in was built small enough and diverse enough that it remained in your mind as you traversed it. You weren't just going through anonymous tunnels, but exploring a space ship where you always had at least a rough idea of where you were.
Mass Effect 3 has a gigantic world, and has you enter, again and again, dungeons that simply start out as holes in the ground with little guidance for the player as to how they're structured, built with repetitive (though high-detail) 3d assets and textures, thus making it necessary to lock things behind you, since there cannot be a reasonable expectation for the player to keep their bearings.