If water temp is above 45 and air temp is above 60 I usually wet wade. It also depends on how far back in I am going. Sometimes if I am roadside, I bring the waders just in case the chill in the air/ wind is a little more than I am expecting.
Wet wading in colder weather- I use neoprene booties, fleece liners and wool/synthetic hiking socks. I'm never uncomfortable like that. As it warms up I Ditch the wool, then replace the fleece with cotton ( more to prevent blisters than anything else)
That's how I do it. Others will their own opinion but I'm happy with that set up.