This is not accurate.

Yes, many election systems result in more parties than FPTP. But left and right still have salience within those.

In fact, you can look at how each politician votes (without explicitly coding votes as left or right). This itself forms a space equal to the number of votes taken. But that vote space can be projected into a much lower dimensional space that captures most of the information about the vote space. If you go so far as to collapse it into a one dimensional space, that corresponds to the traditional left/right axis, and this holds through both history and internationally. The second issue is a bit more varied, but most of the time the left/right axis dominates whatever that second dimension is. Look up DW-NOMINATE for more info.