Pan frying will produce tough meat if the cut is too thin. If the meat was frozen at some point and not well sealed this can a also make beef tough.
I’ve seen London Broil being sold as “steak” before, which I think should be a criminal act as LB in general is a painfully lean piece of cow that needs to be beaten into submission and marinated to be edible. And even then, in serving, it needs to be cut carefully - usually that means slicing it on an angle so the resulting meat fibers aren’t excessively long and stringy. Trying to pan-fry it will lead to sore jaws and tears.
There’s lots of cuts that can be sold as steak, that you certainly wouldn’t want to simply pan fry or grill. Round steak, for instance, needs to be mechanically tenderaized and then can be used for chicken-fried steak. Arm steak and chuck steak are the same way.
“Steak” often refers to the thickness of a cut, not the quality (roast being thicker cut).
Good grilling cuts of steak would included porterhouse, t-bone, Kansas City strip (New York strip), rib eye, and to some extent sirloin.
Basically, any muscle the animal uses actively to walk is going to be tough, along with the brisket.
London Broil was the first thing I thought when I read the OP for all the reasons you’ve mentioned 
You can also treat London Broil as a roast if you don’t wish to marinate it. What I do is coat it with a mixture of Dijon mustard, Montreal steak seasoning, olive oil, and a little red wine before placing it on a rack with a roasting pan underneath to catch the juices. Then I mix up some panko with regular seasoned breadcrumbs and pat that on the top and spray it lightly with Pam so it doesn’t burn. Put it in a 400F oven for maybe 25-30 minutes, depending on how thick it is, and let it rest for a few minutes afterward. Slice thinly at an angle. I swear it’s better than regular roast beef!
I’d say chunk it up and put it through a meat grinder for burgers, but most households don’t have a meat grinder anymore.