Christianity would collapse the day the entire world becomes Christian

I recently had this thought because Christian apologetics seem to rely entirely on comparing themselves to other faiths. Whenever Christians talk about their religion, it always goes like this.

- No other god died for our sins. So ours is the true one.
- Other gods require offerings from you. Our God doesn't require anything. He only gives.
- Other gods require rituals, but ours is a relationship.
- Greek gods vanished because they were just mythology; in the same way, other gods will also vanish someday.

It makes me think that Christianity essentially needs an opponent to define itself. Simply put, the religion would collapse if it no longer had anything to compare itself against.