I've used OVF for 40 years and don't miss them one bit. There is so much more information in an EVF including being able to how the final image will look before you take the photo...something you have to quickly chimp at with an OVF. The new EVF have basically zero blackout...much less than a mirror flapping away. Precision focusing with an EVF is really sweet as you can zoom in with a click of a button and fine tune your focus. I found I had to always use the rear LCD on a DSLR to get precise focus, trying to manually focus using a OVF is a exercise in frustration and using AF with fast lens is just not accurate enough to nail the eye with any reliability.
For fast action sports photography, the Optical Viewfinder will always be king due to zero lag. Canon have said those Customers have insisted they keep it.
The early EVFs were so bad it was a night and day difference. They have improved but every time they hike the EVF pixel count they will need a faster sensor read out and process chain to keep those EVFs near useful for that application. The tiny shutter lag in an OVF is easy to compensate for as the lag free image means the photographer will know where the subject will be. With EVF you looking at where the subject was and that lag is more significant... The high FPS possible with the newest lenses on the A9, will mitigate a bit if the spray and pray style is used in the hope at least one frame will get the shot...
Having said that, and ignoring things like SONY star eating RAW, and the suggestion they are precooking their RAW files to add sharpness, and the issues being discovered with the A9, the A9 will still work for some...
If a sports photographer sold all their old gear for an A9 and found they were shooting at an event where the lighting was going to cause banding, they would be forced back to shutter and the 5fps limit. Not what they spent all that money for...
For a the golf example, the risk is probably far less as any video LEDs that may be present at such an event are likely to be more photo friendly IE not pulse the way the signage LEDs must be pulsing to cause the issue. But most of all for the shots where silence is needed, there is no alternative unless you blimp house a normal camera. The Golf use case is more assured...
The A9 usage has narrowed quiet a bit but for some that will be OK.
This site has more photographers that shoot more static shots, so EVFs have other advantages for them.
The great thing about the DSLRs is you have the best of both worlds. You can use the screen in some shots if needed...
Horses for courses, it is good to have choices...
