There have been some recent performance issues regarding Rayman Legends Definitive Edition on Nintendo Switch. However, you can rest assured that Ubisoft has since dispatched a new update to resolve the issues in an effort to prevent them from resurfacing in the future. Official patch notes from the developer are as follows:
We appreciate your patience concerning performance issues that some of you may have encountered while playing Rayman Legends: Definitive Edition on the Nintendo Switch. This latest patch, available for download now, reduces loading times between levels and fixes frame rate-related issues as well. You should now be gliding much more smoothly through the Glade of Dreams!