CEFR C1
conventionalist
noun
Meaning 1: when discussing person
A person of conventional behaviour or beliefs. It can have more than one sense, so use the alternate meanings and examples to choose the meaning that matches your sentence.
Meaning 2: sense 2
(philosophy) Of, pertaining to, or supporting conventionalism
Meaning 3: sense 3
(philosophy) A supporter or adherent of conventionalism
Meaning 4: sense 4
(history) A member or supporter of the French National Convention