You gotta read it on context my friend, don't just pluck it away in isolation and draw conclusions
Read the previous 8 verses to find out who the "you" is?
Who is God patient towards? Verse 9 says he is patient towards "you", but who is the "you"?
The previous 8 verses answer the question. Follow the pronouns back to the beginning.
2Pe 3:1-8
(1) This is now the second letter that I am writing to
you, beloved. In both of them I am stirring up
your sincere mind by way of reminder,
(2) that
you should remember the predictions of the holy prophets and the commandment of the Lord and Savior through
your apostles,
(3) knowing this first of all, that scoffers will come in the last days with scoffing, following their own sinful desires.
(4) They will say, "Where is the promise of his coming? For ever since the fathers fell asleep, all things are continuing as they were from the beginning of creation."
(5) For they deliberately overlook this fact, that the heavens existed long ago, and the earth was formed out of water and through water by the word of God,
(6) and that by means of these the world that then existed was deluged with water and perished.
(7) But by the same word the heavens and earth that now exist are stored up for fire, being kept until the day of judgment and destruction of the ungodly.
(8) But do not overlook this one fact,
beloved, that with the Lord one day is as a thousand years, and a thousand years as one day.
(9) The Lord is not slow to fulfill his promise as some count slowness, but is patient toward
you, not wishing that
any should perish, but that
all should reach repentance.
Verse 1 says that this is the second letter Peter has written to this group of people called "the beloved". It is this group of people that "God is patient towards, not willing that any perish, but all to reach repentance"
So lets look at the first letter Peter wrote and see who he addresses the letter(s) to:
1Pe 1:1 Peter, an apostle of Jesus Christ,
To those who are elect exiles of the dispersion in Pontus, Galatia, Cappadocia, Asia, and Bithynia,
Peter is writing to God's elect. He tells them scoffers will come, questioning the Lord's return. But Peter says God is patiently waiting for all of His elect to reach repentance. That's why he delays Christ's return. God will lose none of his sheep, every single person that God will save, will be saved, and then Christ will return. God is not willing to lose any of His elect.