Switch has a weaker CPU than PS3 and in portable mode I've heard that its GPU is less powerful than a PS3. It has more ram and a more modern architecture but I don't think that would be enough.
Look at Doom say. It runs at 1080p60fps on PS4 at medium to high settings. It runs at 640p30fps on Switch docked with lower than low settings. That with a very scalable and good engine like Idtech6. Unreal engine 4 games struggle to even run at 30fps at 1080p on PS4, it would get real bad on Switch. There is only so much downgrading possible before the game loses its soul. Those Wii ports of PS3 games felt nothing like the PS3 version. I don't think that is an ideal experience for a Switch owner whose spending $60 on a game.
Even in portable mode, Switch's GPU is better than PS3's. If we look at games they share, like FIFA 18 and Skyrim, Switch performs better both docked and undocked.
Switch ports of PS4/Xbone games wouldn't have to be cut back as much as Wii ports from PS3, because the power gap is much smaller in the former case.