She was more intelligent and talented than her studio ever let her show on camera. She was always cast as the dumb sex object and she was very frustrated with her limitations in that way. She actually had a high IQ and that just goes to show the way women were treated back then. She was never given the chance to be herself or have more complex roles and she was paid far less than her male co-stars. They basically told her "You will always play the bimbo and you have to accept that, we don't care how smart you actually are because men like dumb girls and you need to sell to the audience". I think she achieved as much as she could given her restrictions. But it takes a skilled actress to convince the entire world you are this clueless bimbo when you are not. She was forced to take on a whole different persona that was the opposite of who she really was.
Onscreen she was a "ditzy" blond. Off screen she was quite intelligent. She had a rough childhood, but broke out of it and made a name for herself on the screen. She became typecast and was pretty much stuck with that, even showing that persona when making public appearances. But people who actually knew her all agreed that she was very intelligent and not "ditzy"
Hard to say if it's good acting because she did act very similar off camera as she did on camera so there wasn't a whole lot of "acting" involved. She was pretty crazy but then again a lot of crazy people have been really good actors.
She was a lucky, hot woman back in her era. Talented in mesmerizing and seducing. Nothing more or less. I have not lived in her period of time, but I have made a research. She did experience a harsh childhood and some sexual assaults. She did not know what sexuality was and its power until she found out in her teenage years. Many guys could not stop looking at her breasts, which as a result gave her a great deal of confidence. She became successful because of her beautiful power in making men fall in love with her. That's power!!
Marilyn was amazing but she was always given the "stupid blonde" roles that she grew tired of. She wanted to prove herself as a smart woman. And she was if you read about her personal life. It's a shame she didn't live longer just imagine how many other movies she would have starred in!