He was tailor-made to play in today's NFL. He was the prototype running/passing quarterback. He was also tall, very mobile, and elusive, but the knock on him was that he refused to stay in the pocket as a passer. Something quarterbacks like Patrick Mahomes, Russell Wilson, and Dak Prescott don't always like to do either.
He was ahead of his time as a quarterback, when running backs were the primary weapon. Now, running backs are more blockers and receivers. This is now a passing league with few great running backs playing. In his prime as an Eagles quarterback, he was overshadowed by Philadelphia's Gang Green Defense.
Even as a Cowboys fan back when Cunningham played, I couldn't help but be impressed by his unique abilities. He was very quick, had a strong arm, and was not that easy to bring down.