Absolutely nothing wrong with using stats. Players won't always get good stats, that's nonsense and attackers won't always stand out in those obvious ones
G and A are perfectly fine for some claims and poor for others. Depends what the claim is
If a CM has 10 goals in half a season that's a clear indicator he's performing well
If a CB has barely any headers, that's in most cases poor
Basic stuff
A CM's job isn't to score goals - it's to control games and set the flow of the match, to get the team going. To intercept passes and passing lanes and win the ball too, to set tempo and generally be the engine. A CM can score goals and the team can still function poorly because he is poor qualitatively.
Fernandes is an AM but Man United struggle a lot partly because he is so poor in general play, dribbling, setting tempo, and the short passing game, losing the ball. But he will score a screamer or hit a long pass to create a chance, and guys like you will say he's brilliant.
What is more accurate to say is that you seem the type of guy to think a CM who scores 10 goals in a season is better than a CM who scores none. I don't believe that at all but you probably do.
Headers are not equal to goals. CBs have to win headers because they deal with crosses - heading is a big part of a CB's game. CMs scoring goals is a bonus - it's far from their primary job. Weird comment.