Right, but the point still stands that voting tactically just reinforces the status quo.

Two examples from the last election:

Lisbon, which gets to decide 48 of the seats (the most):

PS (currently leading party) won 21 of the 48 seats in Lisbon. If half their voters actually spread their votes amongst the left, the second-largest party (PSD) would still have only got 13, the IL party 4, and the far right party 4. The power of the right would not have changed, but PS would only have 10 while the left would be a lot more powerful, and we would not have been subjected to a majority victory from PS.

Portalegre, which gets to decide 2 of the seats (the least):

PS won both, with 47% of the votes. PSD won 0 with 23%. In this scenario, if half of the PS votes went to the left, then PS would still have 1, and PSD would also have got 1 - hardly a change on the surface, but the result is that people could look at it and see the other left parties also have some decent representation, maybe it's not crazy to vote for them and they are a viable alternative. Instead, because the votes went all to PS, everyone is now engaged in a self-fulfilling prophecy: "I should vote for PS! Why? Because they're the closest party to the left with a change of winning. Why? Because everyone always votes for PS.".

And that's how you end up with the same two parties in power for 49 years, while everyone is always complaining about how much they suck the whole time and that nothing changes: "We have to vote for X, because not X doesn't have a change of winning, because we're always voting for X; also, not X would probably be just as corrupt and incompetent as X because I'm just guessing they are". I've been hearing that logic since I was a child - the words and rhetoric are ingrained in my brain, and every time I hear the word "elections" the voices pop up in my head.