Even if we use a great UI kit like http://tailwindcss.com and http://tailwindui.com it's not enough to design a product that is simple to use.
What I've seen most makers struggle with so far:
- Validating if your design is good enough before shipping
- Designing a landing page that converts
- Designing a friendly on-boarding process that activates users
- Designing tables and lists and displaying data and actions.
- Designing easy-to-use multi-step user flows
Would love to hear your thoughts!