Reactionary

A reactionary or reactionist is a person or organization that is against social progress and wants society to return to the old way of doing things.
The word reactionary comes from the word "reaction," which describes movement in the opposite direction. In this case, reactionary beliefs and actions are opposed to the direction of social progress.
Some parts of right-wing politics is based on reactionary thinking and a wish to return to the way things were. Being a reactionary should not be confused with being a conservative, which is someone who wishes to keep (conserve) things the way they are.
The words counter-revolutionary or anti-revolutionary are sometimes used instead of the word reactionary.
History.
The word reactionary was first used during the French Revolution. The "réactionnaires" were people who wanted France to return to a monarchy.
20th century.
In the 20th century, socialists and communists used the word reactionary to describe their enemies. In Marxist thinking, a reactionary is someone who supports causes like feudalism, capitalism, fascism, nationalism, or any other cause opposed to social reform and revolution.
21st century.
Reactionary politics is still influential in politics. There are many people and political parties who have opinions that can be seen as reactionary because they want to go back to the old ways. For example, Donald Trump can be considered a reactionary politician.