I can’t construct animals or people using basic shapes, what am I doing wrong?

I’ve been practicing form for a while and the main reason I am is because I hear it’s easier to draw complex things with basic shapes. I hate this advice because I can’t do it for some reason. Whether is be animals or objects they look bad. If I can’t simplify these complex references then what am I supposed to do? Even if I am able to simplify how would I give detail? That’s a problem that I run into also when drawing from reference, whenever the simplifying goes okay, I still find it hard to detail it. What am I doing wrong? What do I need to practice?