The political mechanics of the system result in a two-party system, because no other party ever stands a chance of getting seats. Coalition systems may be less stable, but when you need at least three parties to form a government, they tend to keep each other in check better.
Yes, I know that there are exceptions, but seats should be proportional to the vote. If you have 100 seats, that party only getting 5% of the votes should also have 5% of the seats.
In the country where I live, people do consider themselves leftist, centrists, or right-wing, but a vast majority only decides what specific party to vote during the campaign.
We have the opposite issue, since there is not electoral threshold, we now have a lot of small and middle-sized parties, making it harder to form a coalition. (Would be possible to address with an electoral threshold of 2-5%.)