Cory Doctorow suggests that the ‘ultimate EULA’ is simply “Don’t violate copyright law”. That seems to be a mixture of “Don’t violate an author’s rights”, “Don’t infringe copyright”, and “Obey the law”. The first is sufficient, but it is an admonition, not a license.
A license restores liberty to the purchaser/owner of the copy that is otherwise suspended by copyright.
A license is not a contract of sale, nor a means of the copyright holder being able to reach out and bind passers by.
The purchaser of the copy already has the copy and their liberty (save that derogated from it by copyright). The license can only restore their liberty, in whole or part, even if with conditions. It cannot further suspend the purchaser’s liberty. After all, liberty is inalienable, one could not contract it away even if one wanted to.
A license may also contain or have attached a pro-forma contract that the owner of the copy could agree to at any future date should they wish to (assuming it to be valid), but by the definition of ‘agreement’ or ‘contract’, the purchaser cannot be coerced, or tricked into it by dint of an action they are at liberty to perform in any case.
The shortest license is no license.
The fairest license is a copyleft license.
The shortest, fairest, and simplest license is the libertarian license: You are free to take any liberties you wish with my published work, with but one constraint: The liberties you take may not be withheld from those to whom you give my work (or your combined/derivative work), who you must similarly constrain.
Even better and simpler would be to abolish copyright.