The Republican Party are distinct from the concept of conservative and reactionary politics. They practice both. As do the Democratic Party for that matter. A mental might might be that a party is a group of practitioners and these types of politics are tools they use to accomplish an agenda (though that model implies these tools are amoral and equivalent, which I don't agree with - I find conservative politics unobjectionable, though I tend to disagree with conservative positions, and reactionary politics thoroughly objectionable, as it usually goes hand in hand with bigotry).
It's useful to tease these concepts apart so we can better understand & critique certain policy positions. When Democrats vocally oppose student loan forgiveness, they are practicing conservative politics, for instance. It's not simply that Republicans are reliably conservative and Democrats are reliably progressive.
And there are many other forms of politics, these are just the most prevalent in US politics today.
