How would you define "dramatic need" ?
It's a theatre term, and it describes the internal motivation that drives characters to want what they want. Significant character change usually comes from the character being forced to confront their dramatic need, typically in a moment of crisis.
Here's a well-known example: Peter Parker in Spiderman: Homecoming. What he wants is made clear right away: he wants to become an Avenger. But why? This is not as immediately obvious, but various clues in the film reveal that he is driven by a sense of failure, that he feels a responsibility to use his power to help others and has a dramatic need to prove himself worthy. From his backstory, we know the reason for this - in a moment of selfishness he failed to use his powers responsibly in a way that led to the death of his Uncle Ben, but this is barely alluded to in the film (actually, I think it is only alluded to in Civil War). So now Peter is desperate to prove himself to a surrogate father figure, Tony Stark, and sees becoming an Avenger as validation. This is his dramatic need; it's what drives his decisions right up until the film's crisis.
This allows for character growth that makes the film a lot more interesting than just a bunch of CGI fights. Because Peter's dramatic need, validation, is not what he really needs, it causes him to behave recklessly and undermines him achieving what he wants. Tony recognizes that Peter is not ready and takes the suit away. Peter, ever more desperate to prove himself to his father figure, throws himself into even greater danger and is utterly beaten, left being crushed to death after a failed battle against Vulture. This is the crisis, where Peter has to reckon with his dramatic need and see that it not his real need. His real need is faith in himself, not external validation. This gives him the strength he needs to get out of danger and and defeat Vulture. Tony recognizes that Peter is now ready and prepares to give him what he wanted, membership in the Avengers, but Peter realizes that it's not what he really needs right now and declines. Character growth (change) - by giving up his original want, Peter shows the audience that he has started to understand what he really needs to become fully self-actualized.
So dramatic need is essential to having characters that aren't just stereotypes, that feel like real people whose stories having meaning rather than just plot. It isn't necessary - you can have lots of fun killing monsters and solving mysteries without it - but I think it is essential if you want stories that have depth.