At least five different clients last week asked me if they had to make any changes to their website to get good results from their marketing campaign?
My answer to them was maybe. There are certainly lots of things you can do off your website, like social media, advertising, emails, PR, etc. But, at some point you'll have to turn your attention to your site since that is the hub of your online marketing efforts.
You want your website to deliver a top notch experience that makes people want to contact you, connect with you, buy your products, or take some other action that you want them to take. So, looking at just the off-website factors in your marketing efforts won't get you as good a result as doing both.
Of course, I'm biased since almost everything I do deals with those on-website factors. I'd be curious to hear how others might answer this question?