Because the Switch version was not built on the Frostbite engine (like the PS4/Xbox versions), it is much harder for modders to inject new assets or roster files. Unlike the PC version of FIFA, where you can find massive "FIFA 18 Season 23/24" patches, the Switch ROM scene has very little modification support.
: Earlier updates (like Title Update 3) addressed issues with invisible balls in cinematics, incorrect trainer prompts, and career mode freezes. How to Manually Update on Switch fifa 18 rom nintendo switch update