Purist

[Sonia]

One who aims at excessive purity or nicety, esp. in the
choice of language.

[Julene]

Someone who prefers [the old] way of doing [things].
Someone who adheres strictly to [tradition].

[Justin Bieber]

A person who insists on absolute adherence to traditional rules or structures, especially in language or style.

[Jason Yan]

Someone who wants no change to their favorite video game series. They are the reason why some series become [stagnant] with no new ideas because fanboys whine about them, so when the new games come out, they can complain about how similar it is to predecessor and [thrive on] old games. They contribute absolutely nothing to the future of video games.
While its true that great games should [never change] their formula to the point that it alienates their fans, purists take it too far and seem to be against any good new ideas that may affect their series in one way or the other.

[Monty]

someone who expects everything to be [exactly] like [the thing] they like; doesnt [believe] in watered-down versions of such things

[Merna]

In politics , a [purist] is a person who wants their candidates or social advocates to be pure and exact to their ideologies . They may get mad and criticize their own candidates/ social advocates when they go a bit [off track]. Their candidates / social advocates may even try to [dialogue] with the opposition , something that anger purists . This counts for all political ideologies.

[Justin Bieber]

In sports: [A fan] [blinded] by [nostalgia] who is opposed to any and everything that would make a league better if it means there would be a noticeable change.