Which SaaS is not reactive/offline-first and should be?

Cultivating startup ideas by just asking HN users what they should do is an interesting choice. I'll be paying attention to see how it works.

Notion, please!

I know technically it can work offline, but it lacks so many things that you only can "use" it with internet

YNAB. They use to be a desktop app, but converted it to a SaaS, unfortunately.