That’s true, but only because the German SDP relatively recently (in the 2000s if I understood the Wikipedia article right) adopted neoliberalism as opposed to its historical platform of Keynesian social democracy. For most of their history they were very much non-liberal social democrats.
The way I like to put it is that voting is (one option for) the victory lap. It’s necessary, but will mostly take care of itself if you were successful in your other, vastly more important work. The desperate get out the vote efforts we see today are only like that because they’re the damage control leftists/progressives do after they fail in said vastly more important work (mostly by not showing up).