Leaded fuel is still used in piston airplanes everywhere. While there are ongoing efforts to develop an unleaded alternative, there is none currently available to the market.
There are already multiple unleaded aviation fuels in testing, and one (G100UL) commercially available. The main barrier is that the engines, especially larger and older ones, are not designed to run on unleaded fuel, and must be certified.
Right, hopefully G100UL can replace 100LL reasonably quickly, but there's a big difference between "commercially available" and actually available. I imagine it will be quite some time until it's commonplace for GA aircraft, unfortunately.
If they aren't absolutely essential for some important societal function the aircraft should just be grounded rather than be allowed to fly on leaded. No one's toy or joy ride should be giving thousands of people lead poisoning