I've only been keeping leos for a few decades so maybe I'm not experienced enough to have an opinion.

I keep mine on sand. From the time they hatch until they die.

Occasionally I'll lose a baby, maybe one or two out of a hundred but they may well have had something wrong with them anyway.

As far as leos NOT having sand where they're from, that's a bunch of bullsnot.

Sure, some of the habitat is hard packed clay but some isn't.

If you like sand, use it. If you don't, then don't use it. As far as it being bad for the lizard, I say it isn't.

I wonder how many crickets they find in the wild. Or how many roaches. Or how many beetle larva. Of course, you are free to change the diet they've evolved eating but no no no, don't use the same substrate they did that evolving on because some lackwit lost a gecko or two that was too stupid not to eat sand with it's food.

The thing people forget is that in nature there is a natural culling process and part of that process is that if you are too stupid to not eat sand, you don't get to pass your genes on to the next generation.

I've kept many many many leos on sand and have lost a VERY small number due to impaction.