the Ennet residents who can't quite remember
So have several Ennet residents, though some of them weren’t in much of a position to remember.
Context
The halfway house folded into the roll-call of pond-draining spectators: several Ennet residents have been, "though some of them weren't in much of a position to remember" — the parenthetical placing them, in their using days, among the crowd but not fully present, the addiction erasing the very spectacle they'd stood witness to.