Don't compare TOS and LIS, compare TOS and Irwin Allen's masterpiece: Voyage to the Bottom of the Sea. The resemblence is remarkable. And if you compare Voyage to the Bottom of the Sea (Season 1) to TNG it could be actionable in a court of law.
I'm a huge defender of Roddenberry but he had to borrow some of the elements from Voyage for TOS.
How so? Most of the writing and preproduction of "The Cage" took place prior to Voyage to the Bottom of the Sea's
premier in September of 1964.