No one will be able to tell the difference between 45 mp and 39 mp.
Absolutely yes, when downscaled to the Insta size.
Absolutely no, if you're doing landscapes/architecture, heavy cropping, large prints.
Also, when you upgrade from 5DIV, 45mp sounds like a decent jump on par with Nikon D850 and Sony A7rIII. 39mp is a kinda meh.