I am also working as a contractor and 3-4 year old Angular projects usually are a total mess, there are tons of plugins for simple things and when you want to update npm packages, you basically break the project.

I have found that, using simple JS classes and a small library for example lit.js, makes the project much more understandable and agile after years of code.

Regular fetch and promises, no rx.js and other abstractions on top of it.