That's so clear. Thank you. The words "consumers' solution solves nothing" touched my heart.
However, I have no idea about how to solve the data retention problem except for being open source.
Make it good enough and few people will have that concern, and even fewer will decline to use it because of that. Look at GitHub, Trello, Todoist, and many others; they all started as tiny web apps without much trust.
I should consider whether the early startup even without funding can afford to choose that path.