It is long overdue for the myth that wet feet = blisters to die.
Wet feet do not cause blisters. Warm & wet feet are the problem. Humid feet. Humid feet happen when wearing non-breathable, non-draining, slow-drying footwear that gets wet inside (from rain and/or sweat) and stays wet and warm. The problem is exacerbated, of course, by ill-fitting footwear or sock choice.
Boots, especially waterproof ones, are harder to fit correctly, and more likely to stay wet when they get wet, get humid from sweat on non-rainy days, and cause other foot issues as well.
Absent a true medical need, boots are, in general, overkill - and more problem-prone - for 3-season hiking and backpacking.
Now at this point, I should insert the usual disclaimer..... everyone's feet are different, etc, etc..... sure, yes, true.
But, it drives me a little crazy that newbie hikers/backpackers (common on the camino boards) are still immersed in myths and outdated info about footwear and hiking/packing norms.
Wear boots if you really want to. But don't wear them just because you think you are supposed to.
(fyi - mid-boots don't offer significant ankle protection either. Another myth.)
So I guess my tl;dr answer to your question, "Does anyone have any ideas for how to avoid blisters caused when boots and socks get wet from walking in rain?" would be "Don't wear boots."