Just terrible.
The author seems to conflate not caring about the inconsequential affairs of others with not caring about your own affairs. These are definitely not the same.
Being an "NPC" is considered a bad thing because it is seen as lacking the ability to make your own life better. No serious person cares what others think about them in the abstract, but they do care about what they think about themselves. That's the "lack of autonomy" that comes with an NPC. The fact that the author uses examples like "driving a boring car" or having "a boring job" indicates that they are only accounting for the perception of others in their thought process.
I drive a boring car because I'd get nothing from driving anything more than a boring car. Others, though, DO get something from driving an "exciting" car. Neither approaches to this aspect of life are indicative of being an NPC; they're just facets of each individual's psychology.
What IS being an "NPC" is having a boring job that you don't like, that doesn't pay you enough, that isn't impressive to anyone (including yourself), and that you continue to have because you simply fail to even try to do anything better. That person's situation is terrible. It suggests that if they just had enough capability to introspect and realize that they are an autonomous individual who can put themselves in a better position than they would, but they lack that ability. And to be clear: they don't necessarily lack the capacity to improve their own life, but rather the ability to recognize that they could improve their own life.
The Skyrim blacksmith example is actually a great counterexample. That NPC fundamentally CAN'T change their life. They MUST be content with what they're doing, because even if they weren't, they'd have no choice but to do it. But this isn't what an "NPC" in modern, real-life terms is really referring to. That usage invokes a sentiment that a blacksmith NPC COULD actually change their life if they were just aware enough to decide to do so.
A better example would be the player in Skyrim deciding to simply play the game as intended with no sense of exploration, interest beyond the story presented, or decision making beyond what the developers intended. They just buy the game, play it straight-through, and never pick it up again. Maybe that's sufficient for them, but maybe they're missing out on a better experience because they simply don't consider that a better experience is possible if they just choose to explore another trajectory.
>when you stop caring about being the main character, you finally get to just live your life.
This is good advice for a 14 year old since it's the first step in actually understanding what makes a good life. If you're an adult and you're still framing reality through the lens of video game characters, then you have a ways to go before you should take any of this to heart. There are good reasons to believe you are the "main character," and accepting anything less is a good way to end up a miserable adult who can't figure out why they aren't happy despite having the largest Funko Pop collection in their loose friend group.