Comment by bsimpson
Same is true of home video hardware:
If you plug a Nintendo system's RCA cables into a modern TV, it will look like garbage. Emulated games on LCDs look pixelated.
Those games were designed for a CRT's pixel grid. They don't look right on LCDs, and the upscalers in home theater equipment don't respect that. There are hardware upscalers and software shaders that are specifically designed to replicate a CRT's quirks, to let you better approximate how those games were designed to be played.
Related - someone recently built a CRT dock for his Switch, so he could play Nintendo Switch Online's emulated games as originally intended: