Reddit released a native app and an image host years too late. (I just checked the data and it is not killing Imgur: Reddit image usage was 18% in the top image subreddits at beginning of June, today it is 25%).
The biggest fundamental change Reddit has made in the time since is...making self-posts count for karma. And tracking outbound links.
It really shouldn't be that impossible to have a successful business with hundreds of millions of users. Especially with the wealth of data available to Reddit.