Parties go to the centre because that is where the votes are. You are perfectly at liberty to vote for more minor parties. If you want nationalisation vote communist, clean energy vote green etc. Your vote may not elect a representative but the person who becomes your representative is likely to see which single issue parties received votes in his constituency and act accordingly. Ultimately only one party can govern at a time so it will never be the case that everyone can get their way on the issues they are interested in, but if you don’t vote no one will pay any attention at all.