Poor item selection; very limited options for different quantities; inconvenient location; must pay for membership; crowded stores; long lines.

From the customer point of view, Costco is pretty much the definition of competing on nothing but price: a race to the bottom.

(I know, yes, they pay employees [relatively] well.)

Also their Kirkland signature stuff is to die for. Just saying their in house products often out perform the name brand stuff. Yes it's cheaper and that's still a race to the bottom but they didn't sacrifice employees or quality.

That's not true. I'll buy things at Costco knowing full well that the item is cheaper elsewhere. Why? Because of their excellent customer service and return policy. I know that if that item breaks or has any sort of problem, I can return it no questions asked.

Also, their model is pretty good as far as membership goes -- if you spend enough at Costco, your membership is free, because you get cash back. And a little known fact, even if you don't spend enough to pay for your membership, if you ask them, they will increase your cash back reward to make up for it anyway.

Nobody goes there because it's too popular?

No... People are willing to give up lots for low prices.