“TweetDelete is a service that can mass delete your Twitter posts based on their age or specific text they contain. It can also run automatically on a schedule if you wish.”
–https://tweetdelete.net/
I haven’t tried it, but I read that this can do a rolling delete at a particular time, say 6 months. It seems like it might be useful to some people.
cafebedouin.org 
This is a version of “that which doesn’t kill me only makes me stronger.” I call BS.
The smart move is never to have indulged in a Twitter account in the first place. Backup plan is to delete in its entirety. Of all the deranging influences out there (and there are many), I’d have a hard time assessing which is worst, TW, FB, or IG (insert other candidate here). Because I’ve never had any of them. Was an easy conclusion even at the outset to avoid them all. YMMV.
I stopped using social media in 2017. I kept accounts using the cafebedouin moniker on Twitter, Reddit and elsewhere. But, I didn’t start using them until I got involved with cryptocurrencies last year. The problem with cryptocurrencies is most of the information about them lives on Telegram, Discord, Reddit, Twitter or Medium (the last is definitely of the devil). You have to have accounts and periodically check them to know what is going on. Even for the blog, it is useful to check-in when a page suddenly gets a lot of referrals from somewhere.
In the course of doing that, I’ve found some use for those services. Twitter, for example, is a good way to find weirdos that are weird in ways you like. It’s also not bad for specialists, such as on viruses, war or whatever. So, depending on how you use it, there might be value. But, I do agree that they all should be approached with deep skepticism.
I used the word deranging but other terms such as crazy-making and poison work just as well. No doubt there are some salutary effects for some people using social media, but the big picture described by Jonathan Haidt in particular is one of mental destabilization. While you may regard limited exposure as tolerable and can withstand getting sucked in, that sounds suspiciously to me like “See, it’s only a little bit of poison. Drink!”
The difference between poison and medicine is in the dose.