If you've looked through the rest of my website, you've gathered that I'm heavier on the development and programming side of the industry. However, I do have an eye for good design, and given enough time I can create some decent looking material through trial and error. Design is more than just decoration. People trust good design, and the inverse is true as well. The idea of aesthetics not only attracting customers but gaining their trust is not isolated to the field of digital media.
While that may not be true, it happens anyway. Think about the BMW M6 above. This is a $100,000 car, but you would never pay that price if it was sitting on a sales lot in this condition. The dirty car with missing floor mats and a stain on the passenger seat would be very difficult to sell when sitting next to something shiny of the same class. The dirty car could go another 200k miles and the shiny car could be about to blow a head gasket, but you'd never know it by looking at them. When a person sees something ugly and dirty, the assumption is that it's also ugly and dirty throughout.
The funny thing is that you already know this. You've heard it a million times. "Don't judge a book by it's cover, Perception is reality, All that glitters is not gold", and other proverbs of the same meaning. However, WE STILL DO IT. And it's no different in the digital design and programming world.
You provide your personal details to websites and applications on a regular basis. But when users see poor color choices, form fields that are wonky, a website that's jacked up on mobile view, or outdated imagery they make these assumptions:
The rule applies to not only ugly and outdated design, but it also applies to just poor interface. If the user has to spend an excessive amount of time clicking, searching, and asking questions then you've probably lost the user. If the layout changes on every page and there is no consistent interface, the user will likely become confused. And a confused customer is not a buying customer.
There are a ridiculous number of factors that go into quality design and user interface, and I won't pretend to know them all or attempt an exhaustive list here. The best way to determine if you are behind the times is to look at how your competitors are presenting themselves to the world online. If their car is more shiny than yours, we should probably talk.