The Z80, as well as its contemporary competitor the 6502, are still in production and found as a core in various cheap SoCs for toys and other simple consumer electronics. It's certainly more than enough processing power for a moderately complex calculator, but compare the responsiveness of a TI calculator to the regular Windows (10) calculator running on a machine with several orders of magnitude more processing power --- and the former wins.
I've noticed that programmers who have worked with constrained systems and/or started with low-level languages tend to write better code in general (smaller, faster, often both; and less buggy too) by default than those who haven't; I guess the exposure helps develop an intuition for "how much program/computer ought to be enough" to solve a problem.
I've noticed that programmers who have worked with constrained systems and/or started with low-level languages tend to write better code in general (smaller, faster, often both; and less buggy too) by default than those who haven't; I guess the exposure helps develop an intuition for "how much program/computer ought to be enough" to solve a problem.