> lack of notification method
The way usenet clients worked was when new message headers were downloaded, the client would highlight unread messages. It's pretty similar to email where when you receive new messages, you can tell that they haven't been read before you read them. Websites like Hacker News, Reddit, Facebook, etc lack this feature.
Facebook, for instance, does have a notification system, but makes it very difficult to find the specific reply to your post or comment because it frequently filters out comments from being displayed unless "all comments" is selected from the drop down. Once that selection is made, you have to expand every thread to find the reply to your comment.
> Usenet is a tried-to-be globally governed forum service
Globally governed by whom? The only real governance was the creation of new groups in the Big 8 hierarchy. And, unless the group was moderated, anyone could post or reply to a comment.
> Some server don't allow large attachments, some don't allow HTML message
Text groups had conventions disallowing HTML or attachments, so very few people used them (unless their client wasn't configured properly).
> The protocol don't really help it too. NNTP for example, is neither a high efficient nor resilient protocol. If your mail got too large, or your link is unstable, you'll have some nightmares trying to send it out.
Message size isn't an issue for plain text messages and all major usenet services have no issues handling articles up to 750 Kb in size (for binary groups).
> NNTP is also not a well-designed protocol
What specifically is not well designed?
> NNTP clients (Thunderbird and Outlook)
Outlook never supported NNTP
> will just let the user handle every error encountered
What errors are you specifically referring to?
> So for me, Usenet is just simply outdated. That's all there is to it.
Based on what you've posted, it doesn't seem like you have much if any first hand experience using a NNTP client or have read any of the related RFC documents documenting the NNTP application level protocol.