Hi Alex,
I think that a light meter and your camera's exposure tools are complementary and that it's not a matter of choosing one over the other. If you search this forum (search "light meter" or "Sekonic L758"), you will find many threads in which people talk about using both. I do not share the view that participants in this forum who use both, and cinematographers like Roger Deakins, who Ellory mentions, use a light meter "to look important".
One of the posts above says to forget about a light meter and use your camera and an external monitor instead. Your camera, with a lens and whatever other gear you have attached to it, and an external monitor, make for a bulky, heavy package.
One of the attractions of a light meter is that one can fit in a coat pocket or around one's neck. Uli and Ellory point out that the owner of an iPhone, at a cost of US$45, has a light meter on him whenever he has his phone. The post in which I first mentioned a light meter says, among other things, that a light meter "is a great way to learn about light and exposure. At times, I've carried one around in my pocket, just learning what kind of readings I get in various conditions of light." One can move at ease with one around a set or a street. For example, when outdoors a few readings with a light meter, taking less than a minute, can help speed up filming until the light changes. It can help one focus on getting images and spend less time focusing on data.
Another attraction is that current light meters have displays and computational abilities that make it possible to take a reading and see, just by pushing a button or turning a dial, what happens to exposure if one changes input assumptions such as ISO or aperture/iris. I find that this is a fast, helpful way to work out what my options are. The fact that a meter can average and store readings helps too, not to mention a meter's use in working through ratios. I do not share the view that a light meter presents "difficulties" and "pitfalls" for an "inexperienced user". Indeed, when I started using a dedicated meter I found it both easier to use than a camera meter, although I use that too, and liberating.
Parenthetically, I'd like to suggest that you check out Adorama's show
On Set with Daniel Norton. The show is often about lighting with continuous lights, which are used for filming. Norton, who is a delightful guy and a knowledgeable photographer, also has his own YouTube channel. This is the link for his Adorama programme:
https://www.adorama.com/alc/series/onset-daniel-norton/