Most of us didn't start out being leftists. Lots of us have lib or chud backgrounds but was radicalised by material circumstances and leftist propaganda.
We want more people to turn left and we cannot do anything to change the material conditions of capitalism. We can however work to improve our propaganda so it will have a broader appeal.
To get a discussion going about what is good propaganda we could use our own radicalisation stories as a starting point.
I have always been a weird nerd so for me it was listening to long lectures on YouTube that helped move me from being a succdem to believing that capitalism has to be abolished. Around the time of the financial crash in 2008 Richard Wolff's Capitalism Hits The Fan as well as David Harvey's lectures on Marx was hugely influential in pointing out how capitalism is foundationally incompatible with human progress. Talks by Chomsky helped me realising how thoroughly evil US imperialismnwas and Parenti's content made me question the Cold War propaganda about the USSR and its allies that we are indoctrinated to see as common sense and get a much more nuanced view on things.
I like Dark Souls, so I watched H.Bomberguy's Dark Souls video. That so happened to make me curious about a video thumbnail of a woman discussing incels, so I started watching some Contrapoints, which led me to starting to watching Breadtube. I was hanging around in the "we can probably reform this"/succdem mindset at that point. Then someone there suggested the "Ashes Ashes" podcast and I went "hoooooly shit this system is going to kill us" and then went to the old sub because the quarantine made me curious about how bad could it be, and it all just accelerated from there.