I think accurate polling is more difficult now than ever because people can and do avoid answering the phone or responding to questions however they are delivered. But polling companies, whether they lean left or right, have no incentive to “square” with the customers and tell them that polling now is harder than ever.
But here’s the way that polls “get better” closer to Election Day — they cheat by looking at early voting activity to “true up” their polling. By the time they’ve conducting their final poll in many states, more than 50 percent have voted. And many states identify the number of Democrats and Republicans who have cast ballots. There is no way polling companies don’t use this data to massage their results.
I think the diversity of towns and suburbs contributes to making it more difficult. Back in the day, you pretty much only had to survey one person of Irish/Polish/Scandinavian heritage to know how the town was leaning. Now it’s so diverse, plus .... you can’t get a representative ‘sample size’ of areas, People won’t respond, so the polls are meaningless.