Hard to imagine spinners ever becoming obsolete, but "The Robo giveth and the Robo sendeth away." How much of which it does depends a lot on where and what you're hunting. They've certainly taken much of the need for pinpoint scouting out of dry field mallard hunting, and it's still a rare day when teal turn their tails to them, even late season in areas with spinners on every pond. Spinners toll birds for those who can't manage it with calling and draw attention from those who are poorly concealed, so a lot of folks are better off with them, regardless. Then, too, there are folks who call and hide well, run them all hunt every hunt and feel they're more boon than bane. Others pick and choose their usage.
I'm one of those "others" and only run one more or less continuously for teal hunts or when I've big duck parties that can't, or won't, hide well. Otherwise, I try to keep my Mojo as inconspicuous as possible by using the hen version with the old metal wings that can be rigged to usually stop dark side (which I paint to match the pond water) up when I stop it with a hard-wired remote switch in my permanent morning blind. Unless there aren't any teal in the marsh, I'll generally let it roll until big ducks are spotted, then kill it before I start calling, perhaps flipping it on and off for added draw if calling isn't cutting it. When away from my permanent blind, I don't fool with a spinner at all - with the exception being September teal season, when I might well go to the trouble of packing two in and out.
As for other motion devices, I won't use anything I can't readily control from the blind without giving our location away. I do have a hard-wired Mallard Machine at my permanent blind that eliminates the movement needed to run most jerk cord type rigs, but I find it of limited value and easy to overdo on big ducks, wouldn't fool with it in a less permanent situation and don't miss it a lick when hunting elsewhere.
In any event, of all the motion makers I'm aware of, I believe a judiciously used spinner will prove the most useful for most folks. (Pains me to say that, as I find them as aesthetically pleasing as a flashing neon sign in the pond and not nearly as satisfying to use as more traditional tools and skills.)
If you think I'm wrong, you might be right.