This is very likely true. There are other complex factors, too. I keep seeing polling/forecast methodology explainers mention calibration to historical data so

This is very likely true. There are other complex factors, too. I keep seeing polling/forecast methodology explainers mention calibration to historical data so that if the same method was applied to historical elections then it would have been accurate. But Trump is a way different candidate than any other Republican (or Democrat); he is appealing for reasons that other politicians aren’t. It may be that no historically calibrated forecasting methodology will be accurate when you have a Trump.