WWE 2K18 wasn't a hit on the Nintendo Switch. Its Switch version launched last of the bunch in early December 2017. It was significantly hindered, including only six wrestlers in the ring at once instead of its console and PC counterparts' eight. It suffered from severe frame rate issues, and received a very low score of 35 on the aggregator MetaCritic, contrary to PC, PlayStation 4, and Xbox One's 64 to 67 range.
Possibly as a result of this, 2K Sports are abstaining from a Switch version of the WWE 2K series this year, regarding WWE 2K19's impending release across PS4, Xbox One, and PC on October 9, 2018. In a statement provided to ComicBook earlier today, 2K Sports confirmed that the latest installment won't be coming to Switch with no specific reason why.
2K Sports's statement reads: "WWE 2K19 will not be available on Nintendo Switch. 2K is focused on making the best possible experience for WWE 2K fans and will continue evaluating all opportunities to deliver the franchise across additional platforms." Given WWE 2K18's myriad issues and negative response, it wouldn't be surprising if that was the unspoken reason.
If you're still craving to throw down in the ring though, you can rest easy knowing that WWE 2K19 is still coming to PS4, Xbox One, and PC this fall. AJ Styles was confirmed to be this year's cover star back in June.