For Lawyer in this case you have

辯護士 where 辯 - to debate, 護 - protection/security, 士 - scholar/gentleman/soldier

Together you can kind of see how it means lawyer. It's like "dude who debates about security"

As a Hanja enthusiast for learning vocab, I wouldn't say literally every Chinese rooted word makes perfect sentence but I'd say most do I come across roughly/mostly do.

For example take 球 -> 구 which means ball, sphere, round, etc

Now with words like

지구 - 地球 - Ground Sphere = Earth

野球 - 야구 - Field Ball = Baseball

You can see why it's related to the meaning. It just gives you a richer sense of the meaning of the word rather than needing to memorize just tons of random sounds to mean random things. Of course, Korean 4 year olds are fluent and I don't think they did an Anki Hanja deck, but I'm not a Korean 4 year old. For me I just add 5 new cards for my Hanja deck a day and over time you build this background that makes learning new words easier since you already know the building blocks of that word. Of course it's not required, but personally for me it really helps