The narrative that polling has become much less accurate is more a reflection of media innumeracy than actual reality. Polling accuracy has been fairly constant over time, per a new study in Nature: go.nature.com/2GmIp05
This is a 2-sided problem. Pre 2016, the media overestimated how accurate polling had been all along. It may underestimate it now. Contrary to the media narrative, polls of Brexit and the 2016 US general election were about as accurate as polls had been on average, historically.
Not to say there aren't challenges; declining response rates are a big issue. But if you're citing Brexit or 11/8/16 as examples of failure—when polls were off by only a few points, well within theoretical and empirical margins of error—you may not know what you're talking about.
