Why is this outside the scope of this thread. If we cannot define what a traditionalist IS, how can we answer the question? What exactly IS a traditionalist?
Somewhere else–not on Catholic Answers–I made a point (it had something to do with Patrick Madrid’s critique of the SSPX), that there isn’t a clique on one end of the spectrum whose members can be classed “progressive Catholics”, a clique in the middle called “centrist Catholics” and a clique on the other end called “traditional Catholics”.
It’s much more of a spectrum, and individual Catholics probably shift around quite a bit along that spectrum. I deem myself a “traditionalist” Catholic who wishes that more of my fellow-traditionalists would invest a bit more energy into social issues like poverty and peace. (Many traditionalists seem to have bought into libertarian/neoliberal politico-economic views which I feel at odds with the breadth and depth of Catholic social teaching).
But there are some bedrock consistencies which make the language of “progressive” or “traditional” more meaningful than not. Traditionalists emphasize the Magisterium of the whole Church from Scriptural times to the present, with an especial emphasis on those aspects of Magisterial teaching which are hoary and venerable with tradition. They view innovation, change, and progress with a jaundiced eye–indeed they expect the Church at some point to be infested top-to-bottom with Satanic change-agents seeking to blunt the efectiveness of the Church and to deceive if it were possible the very Elect.
So–without overemphasizing the apocalyptic worries of traditionalists too much–they worry when “the Spirit of Vatican II” ushers in changes and innovations to the way things have been done for centuries, when JPII and BXVI meet in ecumenical gatherings, and even when Francis refuses to wear the red hat, stole, and shoes long emblematic of the pope’s willingness to die for the Faith. It stirs in at least the back of our minds that perhaps the Great Apostasy is upon us, that the Chastisement is soon to befall us, that we might indeed live to see the day of the great ruined city where priests and prelates and a Bishop Dressed In White are martyred on a mountainside.
Apart from this sort of overstated concern: traditionalists emphasize tradition because they believe progress and modernity are sterile, barren, divisive, and caustic. They point to the way even moderately-articulated changes in the post Vatican II era led to declines in vocations, emptying of pews, constant overt dissent, and general malaise. It was the re-emphasis of something more traditional by John Paul II–NOT a traditionalist hero, generally speaking, but giving him his due–furthered by Benedict XVI, which brought a sense of organic wholeness and wholesomeness back to the Body of Christ.
So–traditionalists are those who emphasize tradition out of a belief, whether overtly articulated or inwardly feared–that to depart therefrom may lead to some terrible catastrophe.
Hope this helps a little.