It sounds like an obvious thing to say, but there are so many different kinds of songs and equally, so many different ways to write a song.
I don't go with this "natural and emotional are somehow purer" ethos that many subscribe to. Many of my favourite songs were 'forced' by the writer. As a listener, I could care less. If I like the song, I like the song.
I can't tell if someone was faking it just by listening to a song because there are zillions of different modes of expression, both in performance and songwriting.
As a writer, many of my songs will have a meaning for me that will escape everyone else on the planet. But by the same token, I can also make up rubbish on the spot if I feel inclined. And there's no reason why those sort of meaningless songs won't be as good or engaging as the deep meaningful ones. The other day I drove past a poster that said "The panda made me do it" and within 15 minutes, I sketched out three verses. As I was writing one of the verses I was thinking of Colonel Gadaffi so the song took on sinister overtones. I knew I'd be able to finish it. I forced a melody {I don't think I write good melodies if there's no music already there} and at some point, I'll sit down with the guitar and knock the whole thing into shape.
Trying to write 'about' something specific is kind of hard. But it can be done. I remember once having a great week away with some kids in Wales and because we were staying in a place called Pensarn Harbour, I had a title, "Pensarn in my fingertips" and I definitely wanted to write a song about that trip. But I just couldn't come up with anything. About 2 months later, I was vistiting my Dad abroad. Where he lived, the power lines had been out for 10 months so he had his own generator. But he used to go to bed at about 9 {in those days, I went to bed at 3 in the morning} and turn the generator off so it meant I had to crash out too. So I'm lying there totally awake, hearing all these loud insects and monkeys outside and mosquitoes inside when I decided to see if I could write that song about the trip to Wales. I managed to eke out a first verse and spent a couple of hours just repeating the words so they were lodged in my head. First thing I did when I woke up was remember the verse. It's one of the few times in my life I've ever done that, actually recalled a verse having not previously written it down. Then I wrote it down ! Later my Dad took me to this really boring meeting and I was so bored, I wrote three more verses. It was just the kind of thing that I would have wanted to have written when I was down in Wales. But those were the circumstances it came out. The other three verses were harder to write because I already had the first verse and I thought it was good.
I guess the point is that a versatile writer can act on inspiration or just drag any crap out and make something of it or make something up. But they all count. And the real key is practice.