As others are saying, "8-bit" doesn't mean 8-bit address space. It refers to the ALU "word" size instead - i.e., how many bits you can add, subtract, multiply, or divide in a single step. (Larger types are possible, you just need to do the operations in steps, just like 64-bit math on 32-bit platforms.)
Even in the 1980s, most 8-bit microcomputers had at least 64 kB memory. Today, many AVR chips will have 145 kB of memory (flash + SRAM + EEPROM), and pretty much arbitrarily more can be installed externally.
