According to some propaganda I recently read--and that's a lot more likely to be representative of modern Christian thought, it being what they themselves use to try to rope more people in and all--the sin isn't the same "original sin" stuff that, y'know, is called "original sin". It's a vague, un-detailed sinfulness the origin and nature of which remains ever distant in their explanations. It's just some vague thing like "Man is sinful by nature. Only by accepting Christ can you achieve salvation." Basically, they think of sin like sweat or dead skin cells--your body (or soul, I guess, in this case) just naturally produces it--and they try to sell Jesus et al. as a sort of spiritual shower.
There are entire swaths of Christianity that affirm that a believer only needs--at most--half (the second half) of Bible to "be a christian"--no Adam-and-Eve-originated original sin needed. I agree, naturally, that this explanation is batshit crazy, but, hell, so is the one with "original sin" in it.
The problem is only between dogmatic christians and evolution. The consistently-made objection to evolution by creationists is that it stands in opposition to their sacred scriptures. They see it as being part of a super-global (usually Satan-originated) conspiracy to just be a dick to god by disagreeing with His WordTM.
The whole concept of infinite time before the start of the universe is flawed as proved by Einstein. He discovered that time is connected to space as a single concept which he called Space Time. So before the start of the universe, there was no space and therefore by default, no time. Difficult to get your head around because we as humans live and think in a linear fashion to the extent that to try and imagine 'No Time' is almost impossible.
So if there was no time before the beginning of the Universe, then any creator that exists in time (infinite or otherwise) would have to have instantly appeared to create the universe at the exact moment that the universe (space time) began. This obviously does not make any sense at all because if the creator appeared or 'began' at a specific point in time (namely the very first instant), who or what instigated the 'beginning' of the creator? Who created the creator?