An excellent essay as always, and I believe you have accurately described several of the factors which are making the polls almost useless in this current environment.
However, there is one dire aspect and ominous implication which I believe you have overlooked. The fact that the polling companies have your phone number also means that they have your name and address, they know who you are, they know where you work, etc.
The problem with this is that under the current regime this is an extremely dangerous situation. We have no way of knowing with whom the polling companies are sharing this data. It is entirely possible that these result are being given to certain governmental agencies and freedom-hostile NGO’s and the voters who respond to these polls are being sorted according to criteria such as “favorable” or “unfavorable” to the regime.
People have forgotten how, in the wake of the government takeover of General Motors there were subsequently many dealerships which were forced to close. Closer examination of the statistics of those closings reveal that the vast majority of those forced to close were those who donated primarily to Republican causes and candidates.
The point of all this is that in the currently collapsing state of the rule of law and more brazenly fascist manifestations of the regime, not to mention the many Soros-backed NGO’s who might have influence with your employer, etc., there is real reason to fear expressing your opinions to pollsters because that information might be forwarded to “whomever” and used to threaten your job, family, etc.
I believe you’re correct that the polls are suspect for all the reasons you listed, but I also believe that a genuine element of fear, unease and mistrust is operating as well.