Your users live and breathe on the Web, and expect a certain level of excellence. Make sure your digital properties meet those expectations, otherwise those users will sail towards better waters.
One truth remains: "Content is king". Whether in the form of text, media, or even apps -- quality content is what brings users and then keeps them. Without substance, all you have is fluff.
If content is king, then presentation is queen. Quality content will convince the search engines to bring users to your door, but an attractive, intuitive, and usable interface is what keeps them from bouncing. And yes, all three criteria are crucial.
Keeping your content and visuals loading quickly, efficiently, and with all the latest bells and whistles is no longer a luxury that can be put off. If your website is using old standards, frameworks, and architecture your users will be able to tell.