GSDs were developed in, like, the 1800s to herd sheep and stuff in Germany. They became super popular in the 60s and 70s and, as a consequence, everyone and their mom wanted a GSD puppy. So breeders bred them a lot. And not everyone trained them. So, they did not get a good reputation and still are subject to Breed-Specific Legislation in some areas.
"Old Style GSDs" are a gimmick. Original German Shepherds were lightweight with small ribcages and short furred. So-called "Old-style" GSDs that are marketed today are usually gigantic, long-haired, straightup derpy, and not even authentic. Boo hiss.
American showline (AKC-registered type) GSDs are bred for weird looks. Their sloping backs and clumsy-but-attention-getting gait contribute to poor health and overall lack of physical soundness. German showlines are no better but to the opposite extreme with roach backs being in style. Working lines (mainly European) produce dogs that are more capable and healthy.
The gene that causes the signature Black-saddle-over-tan look in GSDs is thought to be similar to/a mutation of at-- the allele that causes tan points. Tan points is what you see in Doberman Pinschers, Miniature Pinschers, Rottweilers, etc. GSDs can have tan points or have the saddle, sometimes theorized as being as. The puppies start out with just tan points, but as they grow the black recedes and only remains around the base of the skull and back. This isn't proven, but is a cool theories.
"Sable" German Shepherds are generally not genetic sable! Sable is Ay, but most "Sable" GSDs are actually genetically aw: Agouti. This is the same gene and pattern found in wolves.
disclaimer: this stuff is just, like, my opinion, man