I know different artist have different abilities, but why would a comic company even hired someone who did not draw well? I guess I do not understand why the art in comic's is not more consistent.
Well, I'm fairly new to the world of comics, but I will tell you my thoughts. They can obviously draw if they got hired by a company, its just that people have different tastes. Plus, different styles are good for different series. For instance, I just read the Mighty Thor issue 18 and I thought the art was awesome; it was colorful and genuinely Asgardian. I also love the art on the covers of the upcoming Thor: God of Thunder, but the same style can't work with lets say Iron Man. So the quality of the art imo is determined by seeing if the drawing and colors work with the characters and enviroments in the book. It has to be able to capture the feel that the writers want.
Let me preface this with the fact I am new to comics, but I have run across what you mean. While reading Venom I noticed that I wasn't really a big fan of Tony Moore's style for Flash Thompson and Betty Brant. (I think the penciler does most of what you see in comics by the way.) The way Moore draws them they look like they are in their mid thirties. I didn't really give it much thought but I recently bought the Spider Island Trade and Venom and Betty crossed over into the story arc and I was blown away by the difference in Humberto Ramos' take on them. They looked younger and more in line with the characters I thought them for.
As for why the publishers aren't more consistent I think that is because you can only stretch one person so far compared to how many comics do come out. Plus I think they want the art to also set the theme for the story and want variety for different people with different tastes. I would recommend getting Hawkeye and seeing how David Aja's style is. It is vastly different from modern comics. It feels more old school in its style but I LOVE his paneling. Also this one illustrates the need for a cohesive team.The colorist Matt Hollingsworth does a great job with matching the style Aja draws with. Check out Xangel's review where I got this still from.
But this is all me guessing with just my gut intuition on the different jobs and takes between comics haha. Still do I would recommend you getting Hawkeye just to see something very different in this day and age.