Not true at all. Sweden has worse wealth equality than the US. Sure we have high income taxes, but basically no wealth or inheritance taxes. The only reason social democracy ever took off in Scandinavia was due to the fear of the nearby Soviet Union. The moment the Soviet Union collapsed all the countries of Scandinavia started dismantling the welfare and privatising.
Has there been any meaningful change the past 100 years achieved through voting? Every achievement I can think of in the US was won by riots and popular movements.
This will always be the choice for people on the left, at some point you have to bite the bullet and stop supporting right wingers like Biden just because Trump is worse.