"Whoever Wishes"

That something is mentioned last in a book or close to its very end does not mean it is of supreme importance out of all the contents beforehand.  With a book as lengthy and multifaceted as the Bible, which in turn contains many smaller books addressing different matters, this would be all the more the case.  It is still noteworthy that one of the final statements in the entire Bible mentions that whoever wishes can partake in "the free gift of the water of life" (Revelation 22:17).  Earlier tenets of the Bible, such as human moral responsibility and guilt, logically exclude any kind of nonexistence of free will.  A book could say that humans have moral obligations (this is not just the same as saying that morality exists, but it would entail that humans can do what is right and avoid evil) and that they have no free will, but this would be a contradiction.

The Bible teaches moral culpability over and over leading up to Revelation and even in this book itself (9:20-21, 16:8-11).  To be philosophically consistent, the Bible would have to not deny human volition, or else God would be condemning and punishing people for choices they could never make, which would both absolve people of their sin and make God unjust--the latter in particular being utterly heretical since it is God's nature that makes something good (and deviation from it evil).  Of course, a deity who wants everyone to repent (2 Peter 3:9, 1 Timothy 2:3) yet controls people like puppets would be the only obstacle to his own goal, so Calvinism contradicts this crucial soteriological doctrine very plainly.

As if all of this does not already mean Calvinism, the idea that God fatalistically determines who is saved or unsaved before people are even born (or directly forces their wills to any action so that it only seems like they are making free choices), is unbiblical, Revelation 22:17 says that whoever wishes can be saved.  There is no divine pushback in the Bible against God's own will.  Salvation comes from God, who is said to hope for every sinner's repentance in the aforementioned verses.  It would be absolutely contradictory for God to be the causal reason people sin and the causal reason they do not stop sinning.  Aspects of this would be logically possible in isolation, but not all of them at once: for instance, God could force people's wills, but humans could therefore not be guilty of evil because of their incapability of resisting and because of God's nature being what would ground morality to begin with.

Though all language used by others is ambiguous in that one can only know with absolute certainty what one's own words mean, Revelation avoids as much ambiguity as possible by saying that the water of life--a reference to Christ and commitment to him, which is like never thirsting and receiving a spring of water that wells up to eternal life (John 4:13-14)--is something anyone can choose.  An unwilling person will not choose it, yet this is not because they could not have.  It is because they refuse to.  Calvinism denies this.  The Bible does not say people are puppets with only the illusion of free will or that only some people, namely the "elect," have the ability to make choices themselves.  Emphasizing the universality of free will in that every person can turn to salvation if they desire, one of the last verses of the Bible affirms the capacity of every person to repent and align with God.