Question about a Halacha ruling

peace,
I’ve been seeing all sorts of long sentences lately.
For example, I saw a “pamphlet” on head coverings and wigs that was 70 pages long with dozens of opinions, stories, anecdotes, and more (I don’t remember exactly what was in it).
I saw another “pamphlet” about insects in food, and there were also dozens of pages with different opinions, explanations, and things.
I’m studying in a yeshiva and thinking about maybe studying rabbiny and becoming a member of the field, and I don’t understand – for every thing in halacha there are dozens of opinions, anecdotes, history, nuances, and more that need to be learned? How can you encompass all of halacha like that? How many things are there like that? Hundreds? Thousands? More?
What I also don’t understand is that, in everything in the world, if you don’t live it, you don’t really understand it. For example, someone who hasn’t been to the United States or another country abroad won’t really understand the style of Judaism there, which is different from the style of Judaism in Israel. Another example, someone who hasn’t been through things in marriage won’t really understand it, and so on.
Halacha is essentially a halachic reference to realities that occur in life, but how can one rule on halachic matters if it is possible that the person ruling thinks he understands the specific reality but may not understand it at all because he has not lived it or because of a lack of knowledge or for some other reason?
For example, a rabbi can rule that orthopedic surgery must be performed if necessary (logical, right?). But I personally, specifically in this case, have personal experience with this and know that there are surgeries that can be prevented by a number of specific actions related to muscle movement. So a rabbi who simply does not know the field will give an incorrect ruling. And in this case, this is a very significant thing.
This is just an example, I don’t know if it’s successful or not, the point is – how can a rabbi rule if he may not really have the deep understanding of the specific reality. Moreover, he may not be aware at all that the specific reality is broader / deeper / has more nuances than it actually does. That is, he thinks he understands but he really doesn’t understand the specific reality.
Thank you very much.