Almost anymore you need to qualify deep or shallow sand bed. First I like a sand bed because it's more natural and most if not all fish will graze on it. I think you should have enough not to see the bottom because to me it looks odd seeing the bottom and like you didn't plan your set up. The purpose of an aquarium is to replicate the living conditions of the inhabitants. Yet to have seen a glass bottom ocean. I usually have about a four inch sand bed even though in some places it may only be an inch deep due to someone making it's home which is natural which then makes an area a little deeper. I like fish that inhabit the bottom, the middle, and the top of the tank. You might think, Well duh! Well duh.... Some live in the sand during the day and some at night like all the Wrasses you guys seem to love.
You all laugh at the person with castle or bridge in their tank because it........ "doesn't look natural".
If you have problems maintaining a complete system you need to fix the problem. I don't think having sand is the problem.
A problem may be is today no one puts rock in their tanks which is a huge factor in filtration. So they possibly blame the sand for their problems. I love rock in my tanks, watching the fish cruise in and out of it and hopefully new things popping up. And as much as I can fit in my sump.
I add my rock before sand hopefully securing the structure so when someone moves in under an area it doesn't collapse. And having the notion that bacteria in the rock as well as other micro living organisms make their way to the bottom via the rock helping aid any biological mechanism.