I do not really want to defend any of the companies here but the reality is that documentation is always a thankless job. People do it to get their project out there, get limelight and move on. There is not much incentive for the teams to manage the documentation actively unless the its a business priority.

I am myself in the IDP business, was trying to understand the pain points of the user. Even though I am not big fan of AWS but I find that the concerns are baked into the hope that using an IDP would some how make is very easy

> Flexibility of doing local development while on plane

Really depends what you are expecting from the IDP but personally this is one off situation and in most cases its not worth solving. We are in such a interconnected or dependent state where local development without internet is really hard.

> Configuration issue

The features of a solution are two edged sword, it provides people options to tailor it for their own use case and yet at the same time it adds to the learning curve. Good default might have been useful here, however it looks like Author only wanted email and nothing else so it was a departure from defaults

> UI customization

A lot of providers allow some flexibility with the UI but not a whole lot. And then some allow you to host on your website and call the API's for the authentication flows using SDK. Personally this one is tricky, its a UX vs security topic. As a thumb rule never trust the client. The request headers and ability to interact with browsers are what provides you with relatively better state and session control. As an IDP provider I do not want to loose that and still be on the hook for security.