For me, on Verizon, Wifi calling seemed like more trouble than it was worth. I didn't think of the situations with poor signal as wifi calling being an alternative tho. I used to use a Verizon supplied 3G repeater as my signal outside my house was great but inside was almost nonexistent. Verizon attributed it to the foil backed insulation attenuating the signal. Same for Wifi - great inside but nil outside. Signal repeater din;t help much.
Turning off wifi calling and ultimately wifi during calls for me made a huge difference in my overall call quality.
David