And many writers have a bad habit of using dialogue to convey thought when in the real world what we think and the way we express them verbally are many times completely different things.

You want to see some terrible ways this manifests itself on TV?

My son likes DC characters/universe stuff and so for fun I recorded an Episode of the Flash that I saw had King Shark vs. Gorilla Grod (partly because those seem like ridiculous characters to me) and we watched it earlier this week together.

There are multiple times where a group is together and they are "figuring out" an "unknown" in a typical "thinking out loud" scenario.

It's terrible because you want to convey the mentality of their thinking and you want to involve all the characters taking part in the "figuring out" and verbally express it so you get things like.

Character A: But why would XYZ happen unless...

Character B: the real plan was for this to happen because...

Character C: bad guy was behind it all along.

Character A: So what do we do about it?

Character B: Well we could do this one thing...

Character C: and if we do this other thing as well...

Character D (usually enters the scene late just for this one "cherry on top" contribution): Then the world is saved and blah, blah, blah. (followed by some call to action or lead to the next scene).

Bad character dialogue usually stems from a bunch of bad attempts to either portray information or convey thoughts vs. understanding how their character actually talks in real life or naturally would convey their thoughts.

That's all my opinion of course.