The movie used the entire learning experience to add a comedic aspect and pad the runtime. However, with the wisdom of Solomon, he would have instantly known how to use all his powers.
S for the Wisdom of Solomon: Solomon was the third king of united
Israel in historical times. According to the Bible God blessed him
with supernatural wisdom at his ...
Well first of all he broke the staff so he can't create any more "Shazams".
In the comics, sharing his power did not diminish his abilities until Jerry Ordway’s Power of Shazam series.
However, based on the fact that he seemed to be the same after sharing his powers on screen, I think it didn't diminish his abilities.
Supporting the other answers, it bears recalling that in the earliest comics, "SHAZAM" represented an acronym, including the initial S representing "Solomon's wisdom" as a principal part of his power portfolio. There's a nice Captain Marvel themed website with a page inspecting examples from those comics of his mental feats, including: quickly designing a ...
Was the original comic-book version of this superhero also portrayed as lacking in emotional maturity?
There have been many retcons of Shazam! over the years. According to this article
In 1987, a reboot entitled Shazam!: The New Beginning was published, which introduced the idea that Billy Batson retains his childish personality when he transforms into ...
Not from the start of the character but after the post-Crisis relaunch, this became his constant trait:
The first post-Crisis appearance of Captain Marvel was in the 1986 Legends miniseries. In 1987, Captain Marvel appeared as a member of the Justice League in Keith Giffen's and J. M. DeMatteis' relaunch of that title. That same year (spinning off from ...
Christmas features so heavily not because it was originally intended to be released in winter, but because of what the movie is about. It felt like a Christmas movie to the makers.
Jenna Anderson in her January 2019 article for ComicBook.com quotes
David F. Sandberg:
"Yeah, it's all about family and like Christmas time and this family holiday," ...
As the other answers have already pointed out, the wizard ran out of time and was left with only one choice. The AMC Special Edition comic helps slightly, by showing that Billy (inadvertently?) convinces the wizard that he at least has potential.
From Andrew Dyce's January 2019 interview with director David F. Sandberg in screenrant:
Q: Was there a reason that you chose Philadelphia?
Sandberg: Well, we went with Geoff Johns' idea. I think he picked Philly because of Benjamin Franklin and all of that stuff. And the thing about Shazam, or Captain Marvel, is it's been different. It was Fawcett ...
While the story is not a direct adaptation, the movie borrows concepts from a comic by Frank Miller titled The Dark Knight Returns
Here is an article that explores the two works of art (the comic was published first. 10 Times Batman V Superman Directly Used Frank Miller's The Dark Knight Returns
Batman’s Tactics Against Superman
We’ve got to hand ...