[moeamaya]

Agreed Invision can be way too feature rich. Redpen (https://redpen.io/) does an amazing job of filling that void. They boast tens of thousands of paying users, how are you planning to market based on Invision and Redpen as incumbents?

[titel]

For now there is this Show HN submission :D If you have any suggestions about how I should approach this I would love to hear them.

[wastedhours]

Verticalise (I know, I know, give me sh*t for creating jargon...).

Don't go after the generalist approach, focus on a niche where UX or design thinking is a growing area, own the marketing for it, and then you can move to another niche. Perhaps aim at social media agencies looking for creative approval from their clients etc, own a smaller market and grow out from there.