I disagree. Back when Twitter was practically unregulated, it was a lot more popular with normal people and not the weirdos and groomed teenagers who now dominate the site. Most of the people I know irl, and most of the people I interacted with who felt like they had lives outside of twitter, began leaving the site in around 2014-2017. If you look at old accounts (from like 2011), most of them went inactive around that time. This also corresponds with data for worldwide users:
https://www.statista.com/statistics/282087/number-of-monthly-active-twitter-users/
Back in the day, people with swastikas in their names would randomly find your account and start debating race statistics with you, or there would be completely unexpected interactions, like people bantering with ISIS members, celebrities on April 1 posting bait-and-switch videos that had loud sex noises, or Atlanta gang members tracking down an account that was openly posting child porn. There was an element of fun and chaos there that has been lost.
What really killed the site from my experience was the algorithmization of everything, leading to a greater proportion of lunatics, and less opportunity for them to be challenged. In 2015 or so they hid millions of accounts from ever seeing each other, even if they were following each other, based on the data Twitter had gathered over the years. Now you have "communities" as heinous as MAPs (euphemism for pedophile), and a vast mass of hateful edgelord """""communists""""" who can exist without ever being challenged. Nobody talked about twitter with the same kind of derogatory language back when the site was mostly unmoderated.
I actually think 4chan had the same problem during the same period, just without the intentional top-down regulation. Back in 2008 it was just a bunch of people mostly taking the piss. But as the first generation of users grew out of it, it left a greater proportion of people who had no life outside of it, and the general consensus became more and more unpalatable. Even when /pol/ started it wasn't nearly as bad as it is now.
The are other factors of course like the Obama-Trump transition making western media liberals and conservatives permanently lose their minds, taking all online discourse down with them, and the decline in the west of edginess as a political statement. But I don't think that alone explains why Twitter's reputation is so awful now.