Yes, it's impossible to produce, distribute and vaccinate eight billion people for a virus that mutates every few months and one that can persist in animal reservoirs.
When a virus "mutates" it doesn't replace its entire genetic code. A vaccine might work just as well against a new variant if the mutations are in an irrelevant area (e.g. outside the sequence that codes for the spike protein).
Yes it might and it's not all or nothing either. Just like natural immunity can lessen the degree of future mutated infections, vaccine shots can too.
The corona's spike protein though is a simple structure that will likely still infect (be able to get inside a cell) after many kinds of mutations - some of which won't be mitigated with previous vaccinations (mu is leaning this way).
Contrast this with polio which has a Tetris like key that must link up with complex cellular proteins in our cells to enter. Slight mutations in this render it unable to pass through the cell wall. It's why vaccinating for this is so effective and long lived.
Yes, whatever other issues people have with vaccines or especially the politics around them, vaccines do reduce the chance of serious disease. They seem to be less effective than resistance gained through infection, but do protect against delta.
Yes I think this has enough data to support less severity of illness with Delta. And because you are still able to be socially functional with the reduced severity, on average, you'll be out and about spreading it and keeping it alive and changing. This will be an issue when your vaccine immunity wanes and perhaps they don't dial in the next version of the booster to match or get it to you in time
It also depends how many months have elapsed since your last shot, more than five and it seems to be waning in Israel.
With, mu early indications seem to point towards it not working to reduce severity.