Baronlando said:
Indiana Jones is kind of unique ...
I agree. Indiana Jones works as a series because each story is about a specific adventure he has when he takes some time off from teaching. We've seen four of maybe fifteen or twenty adventures. Adventures that don't have to rely on the others. Adventures that work better because they don't rely on each other. Each one is a stand-alone.
Star Trek is very similar in that regard. Individual adventures that the crew goes on when they aren't back in San Francisco doing office work, or whatever it is they do here on Earth. Continuing Education and training, I suppose.
There isn't a tone shift in those two franchises because the tone isn't being rewritten as it goes along.