I do pretty much agree, though there has been some pretty awesome progress in the last 70-100 years, but not usually by people who get much celebrity status (read as: Freud is the best and worst thing to happen to psychology). In cognitive psychology there is quite a lot of more "concrete" science (if that makes sense) going on.
I think the main hurdle is the absurd level of complexity of brains. Although it is sometimes easier to
model psychological phenomena than say physical or chemical, they must necessarily be more complex. I think there are hell of a lot more variables that you have to consider with a psychological experiment, not only that but a huge part of human behaviour is socially based, which makes it even easier to fall into kind of woolly science, as it is basically impossible to test that kind of thing in a lab.
Basically, yeah it's still fledgling, but I think a lot is because the phenomena it is attempting to study are (in my opinion) even more complex than the other sciences it is built on.
Just had a thought while I was writing this also, culture are environment affect cognition, so it could be that even the most basic foundations can/will change over time. Which is really incredibly unhelpful

There was an article I skimmed recently about Facebook use and Dunbar's number (which is the upper limit on the size of a primate social group, correlated with neocortex size, and 150 in humans at the time it was written (70's I believe)). Basically what I gleaned from it (and I admit, I wasn't looking at it as critically as I should have) was that well, you know those people who have 1000+ "friends" on Facebook, and you just think, there is no way they can possibly be actually friends with 1000+ people? Well, you can't, but there was a positive correlation between No. Facebook "friends", the size of an area of the brain (hopefully) related to keeping track of social groups (unsurprising), and the size of their actual social group (somewhat surprising), and that those individuals with extremely high numbers of Facebook "friends" also had social groups larger than predicted by Dunbar (more surprising).
Anyway, I'm sure most of you can see the flaws in that experiment straight off, just think it's interesting, the idea that brain function is modulated by technology and culture, and the implications that has for people trying to study the brain (how much can we rely on past evidence, what kinds of things are modulated by culture that we need to watch out for, what kind of time frame can those changes occur within, what constants are there if any? There probably are constants, btw)
Yup, think that's all I've got for now,
xx
edd