I think there is benefit in considering the many unstated premises / assumptions included in this question before answering it.

The question assumes that God cannot fix the problems. Why should one assume that He can’t? Perhaps He (She, It, They, whatever) simply chooses not to. (Giving free choice. Non-mechanist universe. Mechanist universe.)

It assumes this world needs fixing. Perhaps it’s doing exactly what it’s supposed to do. It’s part of this world’s biology that creatures eat other creatures to survive. Does that need to be fixed?

The question assumes this world is terrible. Is it? It’s also wonderful.

Certainly terrible things happen in this world. Wonderful and amazing things also happen in this world. This world includes dynamic competition between creatures struggling to survive. Viruses and bacteria compete within us all the time. 99.9% of all species that have ever lived are now extinct. Is that terrible? Does it need to be fixed?

Leprosy is a terrible disease. It’s totally curable, but it still exists because of the way Human’s share and allocate resources through our political and national structures. One can give to the Leprosy Mission. How many people do? Perhaps God wants us to “help fix this terrible world” rather than just “fixing” everything Himself so we can all live in …. what … Paradise …. Heaven ….. The Garden of Eden …. Utopia?

People are born, grow up, grow old , and die. Is that terrible?

All life fights an endless unwinnable battle against entropy. Is that terrible?

I recommend watching the excellent film “Pleasantville.”

How could we have a world with no injustice? Would everyone be the same, live the same amount of time, have the same circumstances and abilities? Would you want to live in such a world? Do you want to share your wealth with the 500,000,000 starving ‘untouchable’ Indians who don’t have access to a toilet?

The most terrible thing about this world at present is that over 7 billion Humans are destroying habitat, polluting the environment, and threatening the ecosystems with everything from nuclear holocaust to global warming. We are already something like the third greatest cause of mass extinction in the planet’s history. It’s easy enough for God to fix this terrible world. Just wipe out humanity. Would we actually want that?

Alternatively He could bang 7 billion Human heads together and MAKE us behave sensibly. Would we want that?

Alternatively He could let us develop Artificial Intelligence and wipe ourselves out. Can we be sure He isn’t already doing that?

Perhaps God’s solution to this terrible world is to lead us to view it with greater wisdom.

Hope this helps.