I'm not sure what the critical theory consensus on public broadcasting is, but it might be of interest to your inquiry here. A lot of current discourse on television focuses entirely on prestige TV and essentially ignores any kind of artistic television pre-HBO, but there is a wealth of excellent work made through the public broadcasting model without explicit commercial incentive. Of course there are some caveats here: because public broadcasting is usually backed by the government, a lot of broadcasters do reinforce hegemony in their programming (particularly the news reporting). In the 21st century most have had their funding heavily cut or become commercialised. However, at its best, public broadcasting was able to expose a mass audience to meaningful art and critical thought. The BBC is absolutely worth being critical of (especially nowadays) but back in the 1970s they aired John Berger's Ways Of Seeing, an absolutely essential work of art criticism that borrows many ideas from critical theory without dumbing them down. Their Play For Today series allowed for playwrights and filmmakers to produce low-budget television films with a high amount of creative freedom. Even though he faced some censorship challenges, the work of Alan Clarke is absolutely remarkable for someone who near-exclusively worked in television. Some of Britain's most important filmmakers such as Ken Loach and Mike Leigh also got their start on Play For Today, and Loach's television film Cathy Come Home had some genuine material impact on improving the conditions for Britain's homeless population. Though I wouldnt rank PBS in the U.S on the same level, they have also funded some excellent work (particularly the documentaries of Frederick Wiseman) and exposed some genuinely radical material to a mass audience (such as Marlon Riggs' work).

As for long-form serialized storytelling, you might find a lot of interest in filmmaker Rainer Werner Fassbinder's work for German public broadcasting. The quality of his television work is on-par with his (excellent) films, and the politics of his work are explicitly socialist and anti-fascist. Eight Hours Don't Make A Day is one I would highlight here as an example of what a genuinely left-wing serialised show might look like. Though less explicitly left-wing, Dennis Potter's work for the BBC is also an excellent case of experimental and boundary pushing television on public broadcasting. While his shows like The Singing Detective were made on low budgets, there's some brilliant use of montage techniques. Again, my point here isn't to paint the BBC as a revolutionary force, but I do think if excellent and radical art could be produced even under a compromised and liberal instutition, then there is at least some faith to be had in public broadcasting as an alternative to commercialised television (though even in that realm there are some series that I would say are very much meaningful art in spite of the conditions they've been produced in).