I think there are two issues at play. The first is that many apps don’t use the native share sheet and instead surface their own shittier version, even some Google apps do it which is bizarre - it would be like an Apple app breaking iOS conventions.

The second issue is that most devices also try to be smart about the share sheet and reorder apps based on what they believe is your most likely behavior. So if every weekend when you share a Lemmy image you tend to do it via WhatsApp, the next time you open a Lemmy share sheet it’s likely that WhatsApp will appear first. But once the algorithm starts considering recent notifications and contacts, like some devices do, things can get quite unpredictable.