As I said, intro calculus books will spend a large amount of time teaching you the mechanics of finding closed form solutions for integrals and derivatives of various kinds of functions. Look at https://ocw.mit.edu/courses/res-18-001-calculus-fall-2023/pa... for an example. Most of that content is not that important to understand the concepts.
And yes, with more mathematical maturity you definitely don't need as much detail. The proofs get terser as you're expected to be able to fill out the more straightforward details yourself.
My first calculus class in high school was about 10% "conceptual explanation of limits, derivatives, and integrals", 30% "techniques for evaluating derivatives", 50% "techniques for evaluating integrals", and maybe another 10% (or less) "justifications of the correctness of those techniques". (I guess I'm putting the Fundamental Theorem of Calculus in the the last 10% here.)
The style of this textbook does seem to primarily skip the "techniques for evaluating" stuff, on the basis that you just wanted to understand what each branch of mathematics is about and what kinds of theorems it has that might relate to the larger edifice of mathematics.
And yes, with more mathematical maturity you definitely don't need as much detail. The proofs get terser as you're expected to be able to fill out the more straightforward details yourself.