Freedom of expression inherently includes the freedom to pay for expression. What are your expression worth if you wouldn’t be able to pay a service, cellphone/internet connection/reddit gold to express that? How is paying ads different than paying a campaigner set up a loudspeaker in the middle of a city? But then again, since twitter is a private enterprise, I fully respect their right to act on their own platform.
Cellphones and internet connections are content-neutral pipes that convey content between a willing listener/reader and a speaker they select. So paying for those is a very different case than buying ads, and especially buying false ads.
Especially now that we're 25+ years into the web era, I don't think there's a strong argument for the legal necessity of paid political advertising at all. If I'm curious about candidate or an issue, I can find out anything I want from anybody who can use two thumbs to type something into a box on Facebook or Twitter. I can also get vetted content from a variety of aggregators, from commercial media to non-profit election guides to Wikipedia-style references to my friends sharing things on social media.
Given that, a law saying, "Nobody can pay for reach," certainly wouldn't harm democracy any. And it might help. So I think this is a great step forward on Twitter's part.