Dokku's target audience is developers who want to run web apps. Cloudron's target audience are the users of the app but want to run the app on their server (for privacy, ownership, control, pride etc).
If you are a developer today, you probably make a SaaS product using Dokku/Heroku.
In a Cloudron world, the developer would instead publish the app on the Cloudron Store (https://cloudron.io/appstore.html) and all people who run Cloudron will automatically get this app (no different from how smartphones + appstore works). I can simply click and install your app on _my_ server. Now, currently, people don't self-host because it's too hard to run your own server. Cloudron is trying to fix that.