Here's a recent narrative review of Zone 2 training: https://pubmed.ncbi.nlm.nih.gov/40560504/

They say that most of the evidence about Z2's optimality is from observational studies of high-volume elite athletes, not the general public. They conclude: "current evidence does not support Zone 2 training as the optimal intensity" for lower volume riders and that "prioritizing higher exercise intensities (> Zone 2) is critical to maximize cardiometabolic health benefits."

So, if you like Zome 2, you can do it without mental stress and anguish, and it's fulfilling your goals, continue doing it. If you're stressing cuz your Garmin is telling you you're being unproductive? Ignore your Garmin.