In systems which are parliamentary rather than presidential, there is no such thing as a single candidate (with real power) that’s chosen because there is no single president representing the whole land (or, as in Germany, whilst there is one, it’s purelly symbolic with no actual power).
If the parliamentary election uses proportional vote, once again there are no single candidates being selected: people vote for parties and then seats are allocated in a proportional way, so not voting is perfectly neutral and indirectly favours no party.
Even in systems with parliamentary elections using multiple candidate electoral circles, not voting only sometimes benefits a specific candidate (depending very much on the balance of the other votes).
It’s only when you have single candidate electoral circles or presidential elections (for a position with real power) that not voting for one of the main parties is almost the same as voting for the other one.
Not that I’m defending not voting: personally if and when I find no candidate to my liking I’ll still go and vote, only vote blank, since not voting can just be interpreted as lazy whilst going to the trouble of getting one’s sorry ass of one’s sofa to go and a stand in line and then vote, only to vote blank, most definitelly signals one’s dissatisfaction with all parties/candidates.
It’s extremelly easy for politicians to spin abstention as unimportant, but not so for blank votes.
I’ve actually been a member of political parties in 2 countries (and always small parties, so it’s not as if I’m going personally gain from it) and have even manned voting sections, so it’s not as if I’m not doing far more than average to try and improve the countries I live in.
Then again I can have this far more nouanced take on voting because I generally lived in countries were the voting system meant voting made at least some difference.