Hey, same problem over here had latest iOS 15. Was thinking why not update? It worked fine before the update IPhone Xr and had to try the new features. What ever Tried to reboot it, even factory store, restart and let it have a rest and so on. But still the screen is delayed after touching feels like a ghost has taken over. Has a lot of storage left so it can’t be that’s it’s over used of space None of the solution above worked Hopes Apple fix this bug regretting updating and have been getting support hopefully they maybe help me solve it.