When I was a boy opinion polls were taken by people knocking on doors and asking questions. Then telephone polls came in based on calls calls to landlines and these were regarded as not nearly so good as the traditional polls.
Now telephone polls rare and are regarded as the best but whereas in the 1990s telephone response rates in the US hovered around 36% the rate of response for telephone and email questions is now 1%.
That small 1% is extremely unrepresentative of the general population. Just to take one example it includes a lot of retired or unemployed people who have nothing better to do than answer the telephone to or emails from strangers. And this means that polling companies have to weight the data very much in order to try to make it representative of the population in question. And this means that, in fact, results are pretty fictitious.
This is why the opinion polls did not show that the Democrats would necessarily take the Senate in the election on Tuesday and all the polls before the last U.S. presidential election showed Kamala Harris and Donald Trump as almost exactly even, whereas had the polls been the kind we used to have there would have been some outliers with all sorts of crazy results, which were not true but would have shown that the polling was being conducted in a proper way.
The collapse in response to poll questions affects Europe and the UK as much as America but for a combination of reasons European pollsters are able to be more accurate than their American counterparts.
But individual election polls are of very little use nowadays. Perhaps polls in general are not very useful. What is useful is to look at the polling averages: if a polling average drops a lot over a month, that means something important.

