Firstly, thank you for rejecting the madness of the NCP! Secondly thanks for giving me an opportunity to convince you what socialism is. I am sure you are totally sincere in that offer.
I write as an ex-member of the SPGB, but they have never had a fantasy of perpetual abundance. They absolutely accept the material limitations of our planet.
It was a question that is constantly asked of the party. Hardy did a good job of answering it here.
You are correct that the SPGB does try to convince fellow workers to become socialists. Though it does sound like you rejected them in favour of a Stalinist/Trotskyite party in the past? If so, I hope you have learned your lesson.

https://www.marxists.org/archive/hardcastle/1983/marx_conception1.htm

https://www.marxists.org/archive/hardcastle/1983/marx_conception2.htm