As I understood, this forum doesn't allow to add new features. If you want a new feature, you have to create a proposal on github yourself, even if you never read the ECMA documentation and know nothing about this process, no other way.
This forum is probably only for questions, for other things it is absolutely useless.
To be useful, there should be voting of TC39 members - for or against, and depending on this, adding a new feature.
You can absolutely discuss a potential new feature here - that way you can get a better idea if it's worth the effort to make a proposal, based on the reaction.
Ultimately, changes or additions to the language are proposed by members of the TC39 committee, and decided on during committee meetings several times a year. Non-members can contribute to proposals (you can be a "champion" of a proposal without being part of TC39), but the proposal does require at least one TC39 member to champion it.
So forums like this are useful for discussing an issue, and potentially getting a TC39 member interested in championing a proposal.
Now I understand why many good proposals don't move for years.
1 person may block all.
How many members at all? The more members, the harder to achieve consensus.
Achieving consensus is difficult, but the process helps ensure we don't ship something we can never take back. It's better to go slow then to make something permanently worse.
I'm also not sure that there's any other way to do it besides consensus. If everyone votes for a feature, except, say, whoever represents Chrome is against that feature, well, it would be kind of pointless if everyone except the Chrome team implements the new feature.
I often read through the meeting notes. Usually we're not in a situation where a single person is blocking an entire feature from being implemented. If most people want a feature, and an individual, even if they don't love it, doesn't have overly strong disagreements against it, that individual will usually let it progress.
A lot of those great features you see getting stuck in the proposal pipeline are usually stuck because it's a controversial feature and there's lots of disagreement around it.