"More speech" works when the number of voices is limited to an actual number of people. The truth would eventually/inevitably drown out the conspiracies and disinformation. Now, with bots and social media's algorithmic amplification, the "amount of speech" a single person can contribute is unbounded, and bad actors are weaponizing the unlimited nature of speech to drown out the truth.

"More speech" is too simplistic to work in the modern world.

I strongly agree, also with the factor of energy and rewards: many of the people spreading disinformation have MUCH greater appetite for spreading it, even if it’s not actually their job, than normal people do for debunking it. There’s a burnout problem, especially when the volume of noise overwhelms the rewarding aspects of using a particular forum — less of a Gish Gallop than a Gish Stampede now.

In general, when someone suggests the only solution to "too much free speech" is for people to be filtered, I say "You first."