I take mine (Golden X something) on occasion to Petsmart or Petco or the feed store. He walks quietly at heel and sits when I stop. It’s good for him as a refresher and he LOVES kids. I don’t have any kids, but he’s a kid magnet for some reason, and he sits patiently while they love on him.
I have to be careful, though. He can be dog aggressive if he thinks they are a threat, i.e. running up to him. And unfortunately, many dog owners don’t make their dogs behave in a respectful manner.
And yes, Flexi leads have no place in a public setting. I use one at home, in a rural setting when we walk out to the mailbox or up the road, and my dog is trained not to pull. He get’s sharply corrected when he hits the end, and he knows better. He also has excellent recall, so reeling him in isn’t a problem either. He’s not perfect, so I don’t take him by the road off-leash, just in case he got to chasing something (we have tons of rabbits and other assorted small wildlife) and forgot his ears. He will walk at heel on the Flexi as well as on a regular leash. I don’t like a long line because the excess is a PITA to deal with. My Flexi has a flat nylon lead in it, not rope or string, so I could grab it if need be, but I have never needed to. It’s not the leash; it’s the owner at the end of it that’s generally the problem.