Finishing gaps between drywall panels on ceiling

Those gaps are completely common and not an issue. Pros deal with far worse on almost any job, especially when another crew did the hanging.

You could pre-fill those gaps by skimming and let that dry (or use setting-type compound for a faster job). It'll shrink some, but it'll make the taping coat shrink a lot less. It's not necessary, though.

The fact is that these joints will be stronger than those with just surface finishes. The joint compound pushes through the gap and creates a shear bridge, locking the ends of the sheets together much more effectively than just a thin layer on the face would.