This is one of the major problems of founders who fail to realize that UI/UX is a critical aspect in defining the product's utility even at an initial phase. We worked out on providing feedback to founders who found difficulty in optimizing their UI/UX resulting in an improvement of conversion rate.
I am a co-founder at http://draftss.com and we have shortlisted few important mistakes that founders did on their side projects that could make a significant difference in the purchase decision by prospective customers:

1. Cluttering the website with too much data:
It seems like a dire need for founders to put as much data as possible to explain their product better. But too much data can backfire confusing the customer in understanding what your product is all about. This makes the website look boring, uninteresting & confusing. In such cases using different font weight, size, colors, relevant icons or relevant graphics makes the landing page more meaningful & engaging for the visitor.

2. Using too many colors:
Using many colors randomly on your landing page does not make it look more fancier. Colors are used to differentiate the contents of the website. They facilitate the customer in quick understanding of what the color denotes. Ideally, the easiest way to set up a color palette for your landing page is to use colors from your logo & add complimentary colors to it. For each of these colors, have a lighter & darker tone available which would help you set up a complete color palette for your landing page. It’s best to start creating your landing page once you have set up your color palette.

3. Footer is important:
Many founders did not include a footer on their website. If included, it wasn’t used effectively displaying the relevant navigation to your website. Ideally, you should have a footer which should possibly have all the links from the navbar, and other links which couldn’t be put in the navbar. You should also have social links, even though somebody will not click it but having them builds trust in your website. You should also put some contact details; either email or phone number which adds to the credibility of your website. You can repeat the logo in the footer. This is also an important factor for brand recall. You can convert the logo into a single color and put it in your footer.

4. Missing call to actions:
This is one of the most critical errors that founders missed for their landing page; i.e. not having a call to action near the end of the landing page (just before your footer). This is the point where the customer has been through your complete product and understands what you are all about. It’s the best place where the customer is most likely to buy your product/services. Ideally, all pages redirected from the home page to other important pages must have call to actions too.

5. Unaligned website contents
The content of the website is set to full width and not aligned as per the container. The flow gets lost and the whole page becomes confusing and irritating for the visitor. This will lead to the visitor bouncing off much quicker.

6. Description consistency & balance:
Many products had multiple features to pitch their customers. But each feature had different description lengths between 1-5 lines. This creates an imbalance in the landing page which makes it look fuzzy. All description length must be equal and ideally 2 lines or a maximum of 3 lines.

7. Typography:
Many landing pages had multiple fonts used on the website. Ideally, you should be using 1 or a maximum of 2 font families for your website. Avoid any fancy font for a blob of content. It becomes unreadable and hence more likely for a visitor to bounce off. Most creators use a default line spacing. Adding slightly more line spacing to your text would make it more readable and interesting.

We would be happy to have a look at your side project and share constructive feedback. http://draftss.com/feedback.html