In RIF, any time someone posted a YouTube video or a GIF from various GIF hosting sites, that was displayed directly in the feed, rather than needing to open the link. For articles, it would also choose an image from the article and embed that in the feed, so you could quickly get a sense of what the article was about as you were scrolling.
This is what I'm missing the most from RIF, more so than any button or setting, because it IS the core experience of browsing content in the app. It would open up Lemmy to a whole world of dynamic content, rather than just images and text posts.
I'm guessing this is also one of the more time consuming features to implement, and to that I say—devs, I don't have the skills to help you with this, but I will pay you for it. Right now, it's a barrier to fully enjoying Lemmy as much as Reddit, and I want to stick it to Reddit that badly. DM me if you're interested.
PS: All this is built on the assumption that this is a client-side problem. If it's not, I'll welcome a correction.
[cough]redgif[/cough]