I've had a high degree of satisfaction with AWS but I have done very little with their other APIs. My impression is that Google Cloud is in a class by itself having a difficult API to work with but that's because the authentication process is like the intro to the old Get Smart TV show

https://www.youtube.com/watch?v=ankXUaWqQgM

it seems like LWA is like that for you and maybe that is a big pain point for everything else you are doing. auth is like that because it is so central: if it doesn't work you can't get anything done but boy you are in trouble if somebody can bypass it. I have been reworking an auth system in the last month and it is slow going because the risk is so high.