I have 5D4 and trilogy EF L 2.8 lens and 100-400 IS II and still using nowadays for serious hobby, traveling.
The reasons I don't move to R series yet because it will have to spend a lot of money and my credit card will screaming again for a whole year.
I rather spend my money to something else, coz my 5D and those EF lens still rock.
Maybe when R5 mark II come out I might have a look on it.
24-70 2.8
It's a lens that I'm using mostly all the time