No it isn't hard but it can have a steep learning curve and finding the right resources to learn with can prove troublesome. CSS can be as simple or as complex as you want to make it. As others have said ditch the fancy frameworks and go back to the basics.
At it's heart CSS is a language that sets a style to something. Once you understand that and play with it a bit than you can really start to see how simple CSS can be.
This from Mozilla covers some of the basics CSS basics
Also this from CSS Tricks
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