What I mean is, being good at "Fe" doesn't necessarily mean that you're bad at "Ti". You could be good at both. Or even bad at both. What seems to me is people may have different degrees of strength in logic or emotions or whatever. But it doesn't necessarily mean that if you're good at something, then you'd be worse at something else. I mean you can't be good at EVERYTHING, because resources are limited, but what's considered "good" is in relative strength to others.
At best, I think it's a matter of processing speed and memory. Some people may very quickly solve logical problems or analyze social situations and emotional cues, while for others, it may take a while. But I don't think there's some sort of a fundamental "level" that some people can't reach even in principle. I don't think that Feelers/Thinkers/Intuitives/Sensors are a kind of entirely different "species" that typologies tend to describe in.
Some people may be thorough and methodical, while others are not. It may be because being methodical may take up a lot of mental resources that would otherwise be used for something else. And you could call him a "type", or you could casually refer to him as a "methodical person". But given this premise that I've given, it could be that he would be less methodical and be lazy when he's tired and have no energy left. So if you don't understand the reason why, then you're not going to understand how he's going to act in different circumstances and situations.
Say that Type A has this kind of thinking, and Type B has that kind of thinking.
But how do you, as a 3rd-person observer, understand both Type A and Type B types of thinking? It must mean that you're capable of understanding both, and hence have the ability to use both kind of thinking.
If you say, "Well he's thinking abstractly, but I don't know what the hell he's talking about", then how do you know whether there's some validity to what he's saying, or he's just saying some nonsense?