I would change tomorrow if I felt that one manufacturer's lens line up was more appropriate to my needs……….. long lens are expensive and when you start investing in 400mm f2.8 to 800mm f4 you need to be sure as you can about which is the one for you.
Bodies are not expensive and selling used you can recover 50% + and the same with some lens …… making a "jump" is not as expensive as it may seem
I am a Nikon shooter with a 300mm f4, 300mm f2.8, 70 200mm and 600mm f4 etc., etc.+ + ….. before getting the 600mm I thought seriously about the 5Diii because of the merits of the Canon 600mm f4 versus the Nikon equivalent ….. plus there seems to be more Canon used stuff around as I usually buy used.
What the OP is asking is to have a perfectly reasonable debate as far as equipment is concerned ………. rather than jump on him and make comments that bring his photographic skill into question just discuss the merit and personal preferences of the equipment he is asking about.
I know that we have guys on here who can take marvellous shots with "any" camera, but we are not all like that and some may not even want to be.