At the risk of repeating myself, i'll try restating the point- the problem isn't the choice of voting in-itself, it's the choice of placing rhetorical weight on it at all in a system that is designed to diffuse the political power of the working class to begin with.
The overwhelming majority of liberals will do nothing more than whinge about how unfortunate it is that we live in such a broken system so-long as they remain secure in their personal status within that system. It isn't just about 'overthrowing the government' - it's about stirring the masses into action by raising the issue to such a volume that they can no longer ignore it. That means making it quite clear that democrats writ large risk becoming victims of the fascist movement they helped to create if they continue 'biding their time' until a more convenient moment. It isn't even about boycotting general elections - it's about making it perfectly clear that they cannot count on voters holding their noses indefinitely, and that they do not have a winning coalition without the working class. That will eventually be true no matter what we say as leftists - under late stage capitalism conditions will continue getting worse until eventually enough people will have lost all faith in democracy itself that the only people voting are various factions of the capitalist class and the petty-bourgeois (if we aren't there already, frankly).
Democrats believe that voters may not like the way they govern, but they'll still vote for them anyway to avoid a hostile opposition party. Any popular movement for radical change will be predicated on the notion that nothing short of drastic action will avert that inevitability
The fundamental problem with liberalism is that it makes well-meaning people believe that justice will eventually arrive simply on its own merit, when liberal democracy itself is designed to ensure that popular reform can never happen without organized resistance.