Sony reached their current status by embracing third parties, it took a while but now we have lens, flashes etc available from a broad range of suppliers.
Sony and Fuji, and the L alliance with Leica, Panasonic together with Olympus have very large well established systems.
Canon and Nikon are the new kids on the block for mirrorless. While both are the joint kings of the SLR realm and have been since the 1960’s, they are new to high end mirrorless and are building their systems quickly. There has been a lot of chat about whether these will remain closed systems or welcome third parties.
Well now it seems we know. Canon have issues legal notices to a number of lens manufacturers to stop them from producing lens for the RF mirrorless mount, while we see the first authorised lens from Tamron for Nikon, and we see Nikon executives, carrying the little Zfc with cute Voigtlander primes on the front.
I feel this is sending the wrong signal from Canon, whilst their high end L glass for the new mount has been good the rest is certainly not near the quality of the Nikon Z S branded glass, or Sony’s G and GM glass. Certainly if I was getting into photography now for full frame I would look at Nikon and Sony not Canon. If you have the budget then go Canon for the rest of us Sony have the bigger range and Nikon are knocking it out of the park with their Z lens. If you are into your cropped sensor then neither Nikon or Canon have much to offer from themselves and you are better off looking at Fuji.