Being a guy, I don’t “shop”. I know what I want and then go to get it. Recently I went to a market to get some blackeyed peas and a couple of hamhocks. They didn’t have the beans, so I left and went to another store. I’ll often go to get a certain item and, if they don’t have it, leave without buying anything.
If you can’t get out through the entrance and the carts are chained across the cashier aisles, just say “Excusemepardonmecomingthroughmakeaholesorrypardonme…” and edge your way past the people standing in line.
Or you could climb over the chained carts. If you injure yourself, maybe you can sue the store.
The markets where I shop generally have an open area serviced by two-way doors. One has barriers and a turnstyle, but the checkout lanes that are not in use are only blocked with an unlocked chain.