I always considered myself agnostic leaning atheist. I consider leftism to be antithetical towards religion. All religions have a class structure to them, do priests, rabbis, or imams not exist? And what about marxism, is karl marx not venerated by some leftists in a weird atheist sort of way?
Yes i'd say one of the biggest issue leftist movements get from organised religions is that they have long been used as a mollifier for the working classes, the hope that a persons sacrifices and obedience in this life will be repaid in the next, this leads to obvious problems when agitating for improved conditions if the population has been convinced that their suffering has religious merit. Even though this narrative is less obviously pushed in today's world a lot of that Victorian era moralized work ethic is baked into peoples beliefs today (bootstrapping etc)
Here are two songs I like sung by U. Utah Phillips that were written essentially as a nice simple argument against a reliance on religion to fix our terrestrial issues, a Joe Hill song Preacher and the Slave, and T-Bone Slim's The Lumberjack’s Prayer
The Preacher and the Slave dynamic critique I recall being very present in black communist sharecropper and industrial union organizing in the south in the first half of the 1900s, especially 1930s-1940s, where black workers would hold religious views but had strong criticism of the role middle class preachers had on the communities they worked in. Agreed on aspects of its morality still show up today in people's position, whether it's the moralized work ethic, martyrdom, or a moralist approach to what is best analyzed through the lens of class struggle.
Nice prayer for the second video.