I tend to agree. As I understand it it's the final mile that balloons the cost and in my view a neighborhood collections box is just a micro-optimization. Same with mass dropoff box truck. You're already driving a vehicle with my package nearby just deliver it at that point.
What I want is cheaper shipping if they drop it off at a post office or something. For example on Amazon I see it as an option but only ever as a "carbon-reduction" vs just delivering to my front door. I know it's cheaper - pass on those savings to me.
The irony is that in many cases, it'd take less carbon for them to deliver to your front door than it would for you to get to the post office -- if they're already delivering to someone else near you, their extra distance traveled might be a block or so (or 0 if they were going to drive past your house anyway).
For delivery-to-post-office to be more carbon-efficient than them delivering to your house, the inequality (additional distance you need to travel to get to post office / your mpg) < (additional distance they need to travel to get to your house / their mpg) must be true. If you were gonna drive past the post office anyway, or your vehicle is significantly more efficient than their delivery van, then it might pencil out. If you're making an extra trip, it probably doesn't make sense.