The main thing that is unlike the original hardware is the 128kb memory target and the addition of a mouse. The 64kb era was effectively ushered in with the C64

The main thing that is unlike the original hardware is the 128kb memory target and the addition of a mouse. The 64kb era was effectively ushered in with the C64 and 800XL in 1982, but 128kb came a few years later and concurrent with a market shift to 16-bit CPUs. Accessing that much memory on an 8-bit isn't a natural fit for their addressing capability, even though there are several examples of models shipping with it. (In a lot of ways memory posed a bigger problem than CPU time back then.)