Why not get a woman with the body type of Serena Williams?

Gal gadot could literally kill Serena Williams and probably 99% of people on earth with one hand tied behind her back. I'm a pretty fit dude, but like most people I don't have the training gal does. And I'm pretty sure she could kick my ass and kill me in a few seconds if she had to. This Serena Williams thing is the most desperate hardest trolling I've ever seen.

You are, of course, entitled to your opinion, but I see it this way. Size matters not. When imbued with mystical energies, someone who looks like a hundred pound librarian could do astounding things. And Diana Prince has those abilities. And remember that in Golden Age Superman, it was explained that Superman's body was so much more molecularly dense than Earth people that it gave him super strength and invulnerability.
And then you have Hulk punching a Chitauri war machine and knocking it over. Yes, it is science fiction, but you can do anything in science fiction.

Because in the immortal words of Serge, "that's not sexy."

Wonder Woman is meant to be the ideal Amazon: strong, graceful, charismatic, bold, decent. She has godlike powers but uses them in a manner which supports these characteristics by tackling opponents and conflict situations with mental, emotional and physical finesse.

I don't think there is anyone suitable in the athletics world who could carry off this character. Gal Gadot is a good actress/communicator who also has the aesthetic features of a fit and engaging woman to bring the character alive. Additionally, as previously noted, she has real world experience in a military role so she understands the perspective of a soldier and thus (in combination with the production's choreographer's training sessions) how one might handle weapons and a combat scenario.

Likely another troll post, but I'll play along:

"if we are being real here, these are 'amazonian' women?"
No, if we are being real, there are no Amazonian women.

"Gal Gadot has like zero muscle on her body"
No, she is actually well-toned and fit. Top-level female athletes come in many shapes;Serena Williams is awesome, but so is Maria Sharapova.

"we are supposed to believe she is this strong woman"
No, you're supposed to believe she is magic.

"she was chosen for her looks"
Of course. When a studio invests hundreds of millions of dollars into making and marketing a film, they need a face (and body) that sells tickets and merchandise. When filmmakers cast a character known for her beauty as well as her heroism, they are going to pick someone they find beautiful.

"she looks like some housewife in LA on her way to her yoga class...Not a superhero"
That's why I love living in LA! Not sure how many magical superhero goddesses you know, but all the ones I know look a lot like her.

"there is no way in hell she is doing that... physics are so off"
Yes, usually when one lifts and throws a tank it looks different.

"Look at women who are Olympic athletes"
Search Google for "beautiful Olympic athletes" and click on the images tab, you'll actually see that there are truckloads of really gorgeous women athletes in all shapes and sizes.

"So sick of 'tall white model' being the default female role"
Sounds like a personal problem. But note some of the Amazons weren't white and did have heavily-muscled physiques, most notably real-life champion boxer Ann Wolfe. You might complain a bit that the mythical Amazons didn't all look Greek, either, but I think the filmmakers certainly were certainly aware of your concern and made efforts to represent all types of women with the inclusion of several African and Asian Amazons. Likely every girl in the theater, and quite a few boys, identified with WW. Except you.

When they first announced Gadot in the role, I thought she'd be to skinny for the role. After seeing the movie, I still say she was too skinny for the role. I also think it should've been someone about the the size of a Serena Williams, a Beth Phoenix, or even a Gina Carano. But none of them can act worth a crap.

I'll grudgingly accept Gadot. She did pull the role of nice enough for me to accept her. She's fine as hell, and not too bad a actress.

Amazons are also supposed to remove the right breast to make it easier to use a bow & arrow. That is what the Greeks said anyway, but could be a myth. Still it's a well known part of that Amazon warrior mythology so they should have cast all 1-breasted actresses.

I agree with everything you said actually, but if they went too far off from the comic book appearance, there would be uproar.