Only on the VIC20 and Atari STe. On the VIC20 you had to write the assembler, manually convert it to machine code and enter that into the computer. There was a cartridge with an assembler, debugger and an extra 3.5Kb memory for it but I never got one.
Frankly, if your test suite isn’t catching 95% or more of the bugs, there’s a problem with the test suite and if uat aren’t catching 95% or more of the remainder, there’s a problem with uat
Try Learn CPP or the Beginners course by John Purcell. The later has a really cool project but teaches an older C++ style which doesn’t matter too much as a beginner. Both are free.
People are very resistant to change that reduces their expertise so that doesn’t really surprise me.