Nothing ventured, nothing gained.
The monologues worked because they were a vital part of the story and the writers understood and met the needs of that story. They had nailed the characters down and knew the best way to have them deliver the lines for maximum impact.
And who knows how many times the scripts were rewritten. I'm pretty darn sure the pro's brainstorm and may even write out several different ways of presenting the story. To use flashback or not, monologue or not, action or dialog, linear or non linear. They storyboard and change things until they know they've got it just right.
Just because someone is a newbie writer doesn't mean they shouldn't try a variety of things. You don't really get anywhere writing the exact same thing over and over.
You'll never fly if you don't stretch your wings.
Write the monologue. If it works, great. If it doesn't then change it. Use flashback. If they work fine. If not, change it.
That's what rewrites are for.
Yeah, there is a lot to be said for experience. The pros know what works because they've written stuff that DIDN'T work.
NOBODY starts out a pro. Shane Black was once a beginner writer. So was Tarentino, Ted and Terry, Goldman, who ever.
No matter who they knew or how they broke in, at some point they wrote a rough draft of their very first script.
I think it would be seriously enlightening for all us newbie writers to take a look at some of those drafts.
I imajine though that most of the pro's never want those drafts to see the light of day.
Studios are looking for GREAT scripts.
A newbie will NEVER break in with the same old drivel.
If a writer isn't going to even try and shake things up a little then what is the point?