DLSS2 is not the game-changer some people make it out to be. FSR2 is comparable when upscaling from higher resolutions. Native 1080p reconstructed to 4K via FSR2 delivers comparable image quality to native 4K. Switch 2 using DLSS is hardly going to shrink the gap between it and PS5.
DLSS's real advantage over FSR is upscaling from low resolutions. So for Switch 2's typical native resolutions, DLSS is a lot more suitable than FSR. But for typical PS5 resolutions, FSR2 (and TSR) isn't far behind DLSS2.