I tend to use photon.lemmy.world, but it'd be really cool if I could log in to lemmy.world using tesseract. It's a fork of Photon - so I imagine it also has feature-parity with the official UI - but it's "designed for media-rich feeds and content". It's what they use at dubvee, and db0 also provides it as an alternative
I don't use the default one because it gets confused when lemmy decides to bring a gif in from an external site, and then convert it to a mp4 (it's a pretty hit-and-miss affair in the Gifs Community), though I realise it's ultimately lemmy itself that's causing the problem.
I know what you mean about trailers - I always avoid them for films because of how much they give away. The Ahsoka one isn't too bad, and it's useful as something to refer to as what should be considered a base level of knowledge about a show. Otherwise we end up in the crazy situation of saying that Ahsoka appearing in the new Ahsoka show is a spoiler.
For things that are unarguably spoilers though, the post suggests waiting 'a couple of weeks'. A meme I posted was reported, even though I'd followed the 'usual guidelines' of waiting a week.
We're reluctant to curb people's creativity though, and obviously the thing that's just happened is going to drive much of the original content we especially appreciate. So hopefully, if people follow the suggestion about how best to prevent anyone accidentally seeing something too soon, we can reach some sort of compromise.