Theodicy, the Bare Bones
Theodicy. We want to know why suffering exists, why it persists.
Classically this issue has been phrased as something like "If God is all good and all powerful, why does suffering exist?". The so-called Epicurus Trilemma is:
1. If God is unable to prevent evil, then he is not all-powerful.
2. If God is not willing to prevent evil, then he is not all-good.
3. If God is both willing and able to prevent evil, then why does evil exist?
I will rework this slightly as "If God is all loving and all powerful, why is there suffering?".
To properly engage with this we will need to ask, what is love? Or, more helpfully, within the context of Abrahamic theology and holy text, how is the term "love" used? Except of course, that's an English word, so when these texts use words like ἀγάπη (1 John 4:8), what function is that term serving? Is this term being used in any sense close to how we might use the term "love"?
I think it might be useful to ask a very specific question:
Does God ever do anything that is contrary to what is best for anyone (maximizes their happiness)? Or, does God ever do anything where it is the case that it would have been better for someone, in the long run, if God had not done that thing?
Running alongside side this we might reasonably also ask: is there ever some action that God could take that that would be of benefit to someone (maximizes their happiness)- without harming another - that God does not do? Or is there ever some harm God could prevent to someone that God does not prevent?
When I say that my parents love me, I am communicating, among other factors, that they strive to act in ways that benefit me and strive to avoid acting in ways that harm me (strive to enhance my happiness and decrease my suffering). If someone has no consideration with respect to avoiding behaviors harmful to me, and if they care not about benefiting me, I am not likely to say that this person loves me. And I think this is a very common limiter that most people would place on their usage of the term "love".
So, does God love me, or you, or anyone? You could object that this is not what is meant by love in Christian scripture, or what is meant by ἀγάπη. But it is worth mentioning that, if this is the case, I would call if fair then to say that God does not love humans in any sense even remotely similar to our common usage of the term. I would go so far as to say that in English it would make sense to abandon the phrasing "God loves us" and form some new term to get the job done.
If you wish to maintain that God loves us, and that this is reasonably close to our common usage of the word, then you run into what I think is the central issue of theodicy: it appears to be straightforwardly the case that an omnipotent God could prevent most, if not all, of the harm we humans suffer. Correspondingly, there appears to be much benefit such a God could provide that we do not enjoy. To simplify things, we can ignore examples of humans harming each other (even though I think these are still huge problems that simple appeals to free will don't solve), and just focus on a single example, such as bone cancer, a favorite example of Stephen Fry.
Let's do a little proof.
Premise 1. Bone cancer exists.
Premise 2. God could cure all existing cases of bone cancer and prevent any new cases.
Premise 3. It would reduce harm in humans for God to cure bone cancer and prevent it.
Premise 4. God acts at all times to minimize harm in humans.
Therefore
Conclusion: God has cured all bone cancer and prevents all future cases.
BUT, bone cancer exists and new cases continue to form.
So, if the premises follow through to the conclusion, we have a problem. Premise 1 feels pretty unassailable. Premise 2 seems to be in line with typical Christian theology, although there might be some folks who would go after that one. Premise 4 can't be done away with without trying to insist that God's love for humans is very unlike our typical usage of the term (as discussed above). It seems that the only remaining option would be to go after 3, unless you want to bite the bullet of going after 4.
If one wants to go after 3 you have to somehow argue that bone cancer is good for humans, or at least that God curing and preventing it would be bad for us. You would have to argue that, somehow in the long run, our happiness would be reduced if God were to cure and prevent bone cancer. Someone might also want to discuss the possibility of God selecting among humans: possibly God acts to enhance the happiness of some at the cost of the happiness of others.
Notably, it seems as though some Christians already dismiss 4. It would seem very hard for 5 point Calvinists to maintain that God does everything that could be done to minimize harm to all humans or that He does everything that could be done to maximize the happiness of all humans. To some degree I believe this is why Thomas Talbott ended up embracing universal reconciliation: if the Calvinists believe that a human's final destiny is entirely up to God's decision, without human activity or decisions having any effect, AND God wants to maximize human happiness, THEN God would send everybody to heaven.
At any rate, I suppose one might attempt a response with something to the effect that there are motivations God has that overpower His love, or take priority above it: righteousness or some other factor. If “all loving” were to mean that every act of love that can be taken is taken, and “all righteous” were to mean that every act of righteousness that can be taken is taken and that there are some situations where the loving thing and the righteous thing are mutually exclusive then it could be the case that one could not be all loving and all righteous. Which would be an interesting take.
I think that's everything I have to say.