Am I looking in the wrong place for sharepoint API documentation?

I'm looking for a straight-forward list of Sharepoint REST API endpoints and methods.

So far I've found little tid-bits of information scattered throughout the official documentation.

For example I can't find any documentation about this URI: _api/web/siteusers

Every API I've dealt with has a full list of every possible endpoint and clear examples of how to use them. SharePoint's documentation is all over the place. There doesn't seem to be any clear structure to the documentation.

I mean look at this: Big Commerce API
And then try to figure out how to get a list of brands from a big commerce store.
Answer: https://api.bigcommerce.com/stores/{store_hash}/v3/catalog/brands

And then look at this: SharePoint API
And then try to find a specific site's user by their email address through an HTTP Request.
Answer: https://{TENAT NAME}/.sharepoint.com/sites/{SITE NAME}/_api/web/siteusers/GetByEmail('{EMAIL})

I got that answer from the Power Automate form btw, 90% of everything I've found about sharepoint's API I've gotten from peoples blogs.

Is there some secret documentation that I don't know about? (if its right in my face the whole time, POINT IT OUT PLEASE!)

Is there a way to search Microsoft documentation which doesn't bombard me with 2,000,000 hits that have nothing to do with my query?

I just want clear docs about the various methods:  e.g. "getByTitle('{Title of sharepoint list}')

And the end points for http requests. 

Am I forever doomed to search endless blogs and support forums?

Someone please, throw me a bone.