Complexity. Specifically the complexity of the framework vs the complexity of your need. Often frameworks/libraries solve the whole problem. For example Oauth.

Complexity. Specifically the complexity of the framework vs the complexity of your need. Often frameworks/libraries solve the whole problem. For example Oauth. If you want to provide "login with {Google, Amazon, Apple, Facebook, Instagram, etc}. then you must deal with the differences and oddities of each implementation of the service. And all the different modes of "login with" and then keep up to date with changes. The difference is the same as that between buying a shovel and an excavator. Excavators are fun - at least until you have to fix them - so if you can afford one there is a temptation. Complexity in software is the product killer. The cost of maintaining ten excavator type solutions can kill your product and your productivity, and can require you to create a maintenance department. Libraries and Frameworks are always a temptation and often are useful, but understanding the full cost and all the downsides increasingly makes what seems like an obvious choice not so good. But what if you need only a very basic flow for Github? Do you need that complexity? You may need to expand your solution, so