There is a point of view that regards the requirement for forgiveness as sub-optimal, in the sense that 'If God knew his business, there would be nothing to forgive'. In other words, there are some who think that life ought to be perfect, and if so then there would be no need to forgive, because nothing even sub-optimal (let alone bad) would ever happen.
And some people see Heaven that way. As a place of always-perfection. With zero need for forgiveness.
But I see Heaven as a place of Love, and Love is creative, creation (like Love) is dynamic - and if heaven is a dynamic situation, a place of doing; then it does not make sense to regard Heaven as the kind of perfection that is unvarying, unchanging.
That ends-up with something more like a blissful/ static 'Nirvana' than Christian Heaven - which is made by a personal and loving God for his divine children - who remain persons (and are resurrected, presumably with unique bodies).
My understanding of Heaven is that our main 'work' there (which is also the highest form of play) is to participate in God's on-going loving-creation. Thus Heaven is a place where there are many creators, in addition to God; each an unique person.
This means that all these individual creators need to be brought into harmony; or else there would be a clash and opposition of creative activities - as there is on earth.
My understanding is that this Heavenly harmony of multiple creation is quite naturally achieved by Love. If we have experience of a loving family, we already know that the individuals are continually - quite naturally and spontaneously - making their (creative) contributions to family living within this imperative of Love. So the many acts of many individuals are, over time, harmonised by Love.
But at any given moment-in-time, there are dissonant aspects.
Individuals are motivated by Love - nonetheless, the distal consequences of their love-motivated actions are not wholly predictable - and things may turn out worse than intended, errors will be made; there is need for compensatory correction.
Here in mortal life on earth; our creations are temporary, because every-thing is temporary. So many mistakes and errors of creation just disappear over time. But in Heaven, all the creation is eternal. What then happens to the inevitable errors?
Well, in Heaven errors cannot be erased - but they are compensated. I believe that compensation must be a divine principle.
Of course, compensation is important here on earth as well. As a family member, we may do something, and it turns out badly - we have made an error. Often this cannot be undone, and so we do our best to compensate for it.
That - I assume - is the nature of creation. Creation is full of errors, and full of conpensations.
Over time, mistakes are compensated - but they are still present. Still woven into the fabric of reality...
And this is the reason why forgiveness is vital for Christians.
Love does not lead to perfection, Love cannot prevent all errors. Therefore we can, should - and in Heaven we Do - compentate for our errors (repentance in action!).
Yet those errors remain, and therefore need to be forgiven.
Forgiveness is integral to the functioning of Heaven - Forgiveness is, indeed, integral to Love.
The same happens here in mortal life on earth. There are no 'perfect' parents, siblings or children - and we should not want any such nonsense. But there are (within earthly constraints) Loving family.
(If you must have perfection; then 'the perfect family' is simply a perfectly-loving family.)
Loving parents, sibs or kids will make mistakes - they surely will...
And therefore these mistakes must be forgiven if Family Living is to be maintained - on earth as it is in Heaven.
Indeed loving errors are forgiven, quite naturally and spontaneously, when Love is present and effective. It is only the incomplete and transient nature of love in this earthly life that causes problems. In Heaven, we shall be resurrected to eternal life, with a permanent commitment to Love.
Eternal Love between all persons is what makes Heaven heavenly - and forgiveness is just one of the many consequences.