When voting is treated like the absolutely most important means of political struggle, people do tune out and neglect to organize. The electoral system is a pressure valve, and political theater is a funnel to direct people's rage away from the system itself and towards said pressure valve. Organizing is far more important than voting, yet societal pressures make it seem like the opposite is the case. That is the point Marxists are making, and this is why organizing in a working class party isn't just optional, but necessary for progressive change.
Every major reform and concession has been won through struggle. Not because the ruling class was bested in the marketplace of ideas or anything. The Stonewall Riots were the catalyst for progressive change, not a change in heart in the ruling class. Same as the Civil Rights Movement, where Dr. King was assassinated as he began pivoting not just from anti-racist agitation, but towards the Poor People's Campaign, a growing socialist movement. It's why the Black Panther Party was infiltrated, and its top leaders killed or imprisoned. That's why we need to actually focus our political energies on organized struggle.