The platform of course but I'm aware it would most likely be against their best interest. I don't really have a solution, this is just wishful thinking.
Chronological. Completely uncensored. Allow easy blocking of others, including blocking posts/comments from your personal feed using categories or keyword recognition.
I initially rejected this idea with a reason like "You seem to forget how vile certain parts of the internet can be," but the more I think about it the more I agree, given a few conditions. Namely that children should not be allowed access.
Forbidding children access to the internet would solve many problems, such as social media addiction (potentially leading to depression), the spreading of misinformation, and the general amount of child exploitation online. I don't deny that such an action may introduce other issues that I have yet to consider, but I still feel that the main points are very compelling.
I am also aware that such a system is not perfect and that people will undoubtedly circumvent it, but a much larger number of people will not (if it is made difficult to do so). Unfortunately, the only conceivable way to do such a thing is some kind of age-verification system, which I am against for various privacy-related reasons.
By federating with them, your instance is providing them with free content to profit off of. Every post you make is another post for their users to scroll through, another chance for them to inject ads even if you personally block Threads.
Immediate concern is difference in scale - we're a drop compared to Meta's ocean, and I don't see how we can have any shred of hope moderating the tsunami of content that'll be heading our way.
Long term is EEE. I have zero expectation that Meta would handle a union with the fediverse ethically, and that's their ticket to killing it off before it has the chance to grow into any kind of real competition.
For anyone who's willing to spend ~15 mins on this, I'd encourage you to play TechDirt's simulator game Trust & Safety Tycoon.
While it's hardly comprehensive, it's a fun way of thinking about the balance between needing to remain profitable/solvent whilst also choosing what social values to promote.
It's really easy to say "they should do [x]", but sometimes that's not what your investors want, or it has a toll in other ways.
Personally, I want to see more action on disinformation. In my mind, that is the single biggest vulnerability that can be exploited with almost no repurcussions, and the world is facing some important public decisions (e.g. elections). I don't pretend to know the specific solution, but it's an area that needs way more investment and recognition than it currently gets.
Funding/resourcing is obviously challenging, but I think there are things that can support it:
State it publicly as a proud position. Other platforms are too eager to promote "free speech" at all costs, when in fact they are private companies that can impose whatever rules they want. Stating a firm position doesn't cost anything at all, whilst also playing a role in attracting a certain kind of user and giving them confidence to report things that are dodgy.
Leverage AI. LLMs and other types of AI tools can be used to detect bots, deepfakes and apply sentiment analysis on written posts. Obviously it's not perfect and will require human oversight, but it can be an enormous help so staff can see things faster that they otherwise might miss.
Punish offenders. Acknowledging complexities with how to enforce it consistently, there are still things you can do to remove the most egregious bad actors from the platform and signal to others.
Price it in. If you know that you need humans to enforce the rules, then build it into your advertising fees (or other revenue streams) and sell it as a feature (e.g.: companies pay extra so they don't have to worry about reputational damage when their product appears next to racists etc). The workforce you need isn't that large compared to the revenue these platforms can potentially generate.
I don't mean to suggest it's easy or failsafe. But it's what I would do.
The ultimate social media site, in my perspective, would probably have the simplicity and functionality of Side 7, the content execution methodology of TV Tropes, the expandability of Discord, the rule enforcement of ProBoards, the fanbase of YouTube, the adaptability of Hypothesis, and the funding of Pogo (classic Pogo, not modern Pogo, and no I don't mean Pokémon Go).