Adding restrictions on who can be granted Moderator status will not solve the underlying problem; a streamer who doesn't pay adequate attention or take adequate care in who they grant authority.

It's funny that you say such a feature seems "very simple and obvious", given the lack of common sense that you're arguing warrants such a feature.

While it is important to prevent trolling and other issues on Twitch channels, implementing strict requirements for becoming a moderator may not necessarily solve these problems. Setting a minimum time of account creation may not be the most effective way to determine the trustworthiness of a potential moderator, as it is possible for someone with an older account to have malicious intent. Moreover, strict requirements may create a barrier to entry for smaller or newer channels, limiting their ability to attract qualified moderators.
Some mods like to make channel-specific accounts so they can mod anonymously.

Instead, channels may benefit from implementing a more comprehensive screening process for potential moderators. This could include a review of their previous moderation experience, their behaviour in the community, and their ability to handle conflict effectively. This would help ensure that only qualified individuals are given moderator privileges, without limiting the pool of potential moderators unnecessarily. Maybe a rating feature or a badge like "verified mod" or something like that.

In addition, it should be common sense not to grant moderator privileges to someone just because they have donated to the channel. While donations are certainly appreciated, they should not be the sole criteria for becoming a moderator. A good moderator should be able to enforce the channel's rules impartially, handle conflict calmly and effectively, and communicate clearly with the channel owner and other moderators.

Therefore, it is important for streamers to choose qualified and committed individuals to serve as moderators, based on their qualifications and experience. By doing so, streamers can help ensure the success and growth of their channel over the long term.

I would like to see different levels of mods - Community helper - Moderator and Channel admin, each with different perms ( admin being the highest ) that way mods can be well... moderated without the channel owner having to interrupt stream.

I have seen multiple new streamers be talked into modding a scammer account who then blocks everyone out of the chat that doesn't go along with the scam.

Moderators need to have accounts that are older than 10 days at least.

Good idea, but instead of being a general time, it is better if it is the time you have been following the channel (to be moderator of the channel you will need to follow it for 3 days or more).