A little unfair to compare the MG4 to a Tesla. Not really in the same league. Having sat as a passenger in a Model 3 and driven a Model Y, I can say that I was pretty impressed though. Would I swap my current car for one? Unlikely. I certainly wouldn't swap to a MG4, but would recommend a Tesla if buying used.
However, it does show buying a used car is still very much a viable route. I've not bought a brand-new car since 2000. All have been 2 to 3 year old. Only ever had minor issues that have always been sorted quickly. Only my BWW 3 series let me down a few years ago, which I had to sell 6 months in.
I do worry for MG4 though when the used market eventually becomes popular as I think these first generation cars won't have much longevity despite the 7 year warranty. The drivers seat to me on the SR didn't look like it would last very long.
Enjoy the Tesla though, I still believe it's the best EV out there.