“It’s 50% probability. Either it’s true or it isn’t.” — what meddlers pretend when they’re not happy admitting the high probability of their enemy candidate being elected. It wasn’t a coin flip.
Polls always need to be skewed in some way to be accurate, since not everybody will vote. You can't just get a random distribution of the population's preference and assume the more-preferred candidate will win. Polls can never be truly accurate because people will lie about which candidate they're voting for and whether they're planning to vote, and sometimes people who genuinely intended to vote never make it to the polls. There are a huge number of variables to consider when trying to predict the outcome of the election, but it's important enough that it's still worth trying.