When is noise reduction 'too much' and ADR is the only way?

Hey everyone, I'm cutting a doc right now, shot mostly on an FX30 and Pocket Cinema Camera 6K G2, where we were often in pretty dynamic environments. Think busy markets, windy outdoor interviews, even some tight indoor spaces with HVAC hum. I've been using noise reduction pretty actively to clean up dialogue recorded on an MKH 8060, and it's definitely helping. However, I'm hitting a wall sometimes where more noise reduction starts to degrade the voice. I’m finding myself constantly battling between making it intelligible and making it sound unnatural or thin. I know over-processing is a common pitfall. For those who've been doing this longer, how do you practically draw that line? When do you decide, 'Okay, this is beyond noise reduction, we need to consider ADR,' versus just accepting a certain level of background noise? What's your internal threshold for kicking something back for ADR?