unlike the C64, the CoCo used normal, consumer level cassette machines
The problem I had was tape reliability
And now you know why the C=64 didn't use consumer tape recorders.
Ordinary tape recorder speed and volume of recording can vary from machine to machine. The 64's datasette was more strictly engineered, for compatibility between systems.
It's why on CP/M machines, you could hook up a generic tape recorder to record your programs, or you could spend extra money for a "data" cassette recorder, which helped improve reliability.
(The C=64 part is according to what I've read. I never had a datasette for it. I was one of the fortunate who started out right with a 1541.)