Nope - that's not correct: saying "there shouldn't be any pizza party" is a vote! If more than 50% of the people invited at the party say: "We should actually get salad!" - then, guess what? You would get salad.
Being silent - not voting - is NOT the same as voting against something. Not even close.
If the real reason for why over 50% of the people don't vote was because they don't like any of the parties then they could join up and create an alternative. But this is not what happens.
In the real world when you don't vote you're doing two things:
1 - you're saying you don't care because you find all the options not to your liking;
2 - you're also saying you can't be bothered with creating one.
As long as none is preventing you with addressing the second part: you are making a deliberate choice to not engage in the democratic process. You understand the consequences of that (in)action and you accept them. In no way that invalidates the choices made by the people who engage in it.
Saying that you CHOOSING not participate in the process makes it invalid is an offence to the people who fought to give you that choice and to the people that - to this date - are not given that option.
I'll say this one last time: this defeatist attitude towards the democratic process is exactly what the political establishment and the lobbies who enrich them are counting on, and this is why I considered it one of the main issues with democracy today.
The Official Monster Raving Loony Party [0] is doing more for the cause of democracy than people who decide that nothing is going to change, we are going to get anchovy pizza, so why bother with voting.
[0] https://en.wikipedia.org/wiki/Official_Monster_Raving_Loony_...
Edit: Fixed typo - twice