Honestly overall Nintendo did a great job with the Switch 2 just improving on alot of the complaints and biggest issues with Switch 1 such as Joy Cons, build quality, specs, backwards compatibility, and features such as voice chat. However, there's still some stuff that has left to be desired.
I still wish the UI and the system itself has at least some sort of personality and feel like previous Nintendo consoles like the Wii, Wii U, & 3DS. Make the console feel memorable outside of just the games.
Battery life I wish was also better, its not so much that I just want to play the system for more than 2 hours, but I want to automatically play the system with at least a decent chunk of battery left and I dont really feel that with Switch 2 over Switch Oled.
Of course I do miss an Oled display as well, while Switch 2 screen is still definitely an improvement, its not as big of an improvement you'd expect or desire for a system that came out 8 years after the predecessor. Although 120hz is definitely great to have.
Also, this probably isnt a problem with the console itself, but I still feel like Nintendo could be doing better getting 3rd party support on the Switch 2 faster. Like its surprising we have yet to see anything major from Microsoft yet after being a good supporter for Switch 1 and publicly confirming their support for Switch 2, even COD wasn't released yet on Switch 2 while the PS4 still got a port and that game is under contract to release for Switch 2. Other 3rd party developers I expected a bit more rapid support too. It could be that for some reason Nintendo decided to limit sending development kits specifically for Switch 2, or maybe 3rd parties aren't going to support Switch 2 as much as I thought, so yea that's one potential flaw.