The Switch using an "old chip" is not true. Relative to the portable chips that were available at the time the Tegra X1 was as cutting edge as the PS4 or XB1 were. Switch is more in line technology wise with the N64 and GameCube. They were aiming for a 2016 launch too, 2017 only happened because they needed a couple extra months for software.
Tegra X1 launched back in 2015, Tegra X2 a year after. Switch came out two years later using the X1 launch (using Maxwell). Pascal GPU's was already out by the time Switch was available to buy. And that is a whole generational leap. Like I said, they like tried and tested mobile technology that has been used and applied on other products. It has been shown historically again and again with the DS, 3DS etc. They like to play it safe and won't go with cutting edge.
Yeah, its quite impressive to see those games on those handheld but that's it. Only ports from old gen past and some other ones this gen. If they only went with Tegra X2 it would have been a beastly handheld.
As great as DLSS is, we have no idea if the new Switch will support it. Hell, they might even use another SoC altogether. All I can say is no mobile technology is going to reach equivalent performance of PS5/Xbox Series X in a few years.