Wii U and 3DS both sold less hardware than GameCube and GBA while also taking hardware losses at some point.
The only other era you could argue was on par or worse was GameCube+GBA, but again I already gave the reason why that isn't the case.
Digital distribution didn't exist for GameCube and GBA (or really anything at that time besides starting to slowly emerge on PC), so I suppose if someone can show me software profits you could make an argument that Wii U+3DS fared better than GameCube+GBA due to digital software sales that yield a higher profit for Nintendo.
N64+late GB/GBC was not an overly successful era either when compared to Switch or Wii+DS but Pokemon was a global phenomenon that carried that era massively. If Nintendo had no Pokemon and just coasted on Game Boy during that era without Game Boy Color, that would likely be the worst era because N64 had disappointing sales and the Game Boy would be dying.
Lifetime Sales Predictions
Switch: 161 million (was 73 million, then 96 million, then 113 million, then 125 million, then 144 million, then 151 million, then 156 million)
PS5: 115 million (was 105 million) Xbox Series S/X: 48 million (was 60 million, then 67 million, then 57 million)
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima
