I don't think it is. It is very clear that Peter is very motivated indeed, and it is easy to identify with his motivation. There is nothing unclear about his characterisation at all.
I think it is quite specific, actually; as has been pointed out above, one of his points of motivation is that he is trying to show his father figure that he is worth his love. It's actually a little heartbreaking that it's Tony Stark of all people that he's trying to show that to...
Anyway: Yes, this is "normal" motivation, something that could be anyone's background. But the thing is that in terms of the superhero genre, it's actually the opposite of "generic", because that's never the origin*. It's actually a new approach, not showing the tragic death that motivates the young hero.
That being said, though, I do think we experience his motivation going further than said everyday psychology. The scene after Keaton warns him off is very well done - this is the moment he should've caved, especially with him threatening Aunt May and being Liz's father and all that. And he's had to give up on being an Avenger anyway. So what is it that keeps him going? The moment is interestingly filmed, too - he almost seems catatonic, in a trance. And then he's made his decision.
I think that moment hints at his deeper motivation that runs underneath the layers of, you know, a kid dreaming of being a superhero and wanting to find a father figure.
What I'm trying to say here is, showing instead of telling is an old rule of storytelling, and it's working here. The writing actually is quite crafty, whether you agree with the decision they made or not.
*Well, I expect it actually has been in a lot of comic books at this point. But it's quite new to the movie audience.