Would I be wasting my money to get a turntable?

What do you call the conversion of an analogue signal to a PWM/PDM or ΔΣ modulation and its subsequent filtering to recover an amplified analogue signal? Because if that’s not digital, then CD is not digital and streaming is not digital either. However, that’s exactly what happens in a class-D amp, at some point. The filtering is at the very end, but the signal conversion can happen at the amp input or just before the final (current) amplification stage.

In class D amplifier "Voltage" is converted to "Duty Cycle", both analog - meaning there is no discrete steps (unlimited resolution).  Duty cycle is back-converted to (amplified) voltage by filtering.  Streaming and CDs both have limited resolution (16 bit in CDs).

What happens when your PWM’s oscillator signal frequency is not high enough?

This frequency, likely >0.5MHz limits amp's bandwidth.  My older Icepower was limited to 60kHz, resulting in 20deg phase delay at 20kHz.  It can affect summing of the highest harmonics (that I cannot hear anyway).  Zobel network on the output leaves about 1% of the ripple, but the membranes at this frequency don't move.  This 0.5MHz frequency is about 100 times higher than highest root frequency in music resulting in practically unlimited resolution.  I agree, there are limitations of class D, like of any other class - I was just stressing, that the fact of switching output between two voltage values doesn't make it digital since these constant voltages are not the quantity of interest at this point (duty cycle is).