Midrash makes for far more 2-dimensional people than you have in peshat.

Let me explain with a mashal. The first Star Wars series was a classic Hero’s Journey plotline. And the characters — good was good, evil was evil. Everything was very black-and-white. This mythic style of storytelling uses characters as archetypes.

The most recent trilogy didn’t preserve this. People today don’t want mythos; they want character development. They want a Luke Skywalker with some dark in his past. Luke ceased being a symbol because that’s not what the current market wants. (How many superheroes were given dark sides in the past 30 years?)

Midrash adopts the more mythic style. Reuvein and David are good guys, so Chazal enforce a perspective in which “whomever says Reuvein” — or David — “sinned is nothing but in error.”

Pinechas and Eliyahu’s stories are told to make them a single archetype of qana’us, and so to get the full picture of the role of qana’us in our own lives, we need to combine the two into a single mental image. But Pinechas and Eliyahu as real people were more than their qana’us. This kind of collapse is about collapsing them into a single idea to teach about it.

So, the Torah’s portrayal of characters are emotionally and morally more complex than Chazal’s. Even if Chazal provide us with more detail than the pasuq does, I called that more “two dimensional”.

I recommend also seeing my earlier post Aggadic Stories, History and Halakhah. I make different points, but the topics overlap. There, the subject is whether we should take such stories as historical, and if not, does it change how we deal with questions about them from morality or halakhah? Until the 19th or 20th century Counter-Reformation, there is a consistent position among rishonim and acharonim that retelling a midrash says nothing about whether it historically happened or not.

The point of a midrash is to teach you how to live. As long as that is done without besmirching tzadiqim or otherwise violating halakhah, they would retell the story. Which means that we could even derive halakhah from the stories without knowing whether this particular one was historical, since no tanna would retel a story in which a navi sinned.

I think it’s better to think of the historical Avraham, the Torah’s Avraham, and midrash‘s Avraham — and even various tannaim‘s and amora’im‘s own Avrahams — as different narratives. Even though I believe the Chumash‘s version is historical, there is much in what Hashem chose to focus on, and what He chose to omit. It’s but one way to look at and understand the historical Avraham. A useful way for what Hashem wants of us, but perhaps not the way people who encountered him would have.

The midrashic versions… I wouldn’t say they are giving detail atop Tanakh’s version. They are teaching lessons atop the ones the peshat in Tanakh does, but using a very different narrative style and thus a different story, and not even exclusively sticking to the facts the way Tanakh would.