I'm a pretty enthusiastic hobby photographer, and I jumped on mirrorless systems + EVFs several years back. On the Olympus OM-D E-M10 (and what IS it with Japanese electronics companies and ridiculous nomenclature?), the EVF was absolutely never a problem EXCEPT in that it impacted battery life a bit (solution: a second battery in your pocket).

I upgraded last year to a Sony A7ii, and this one's even better.

The tl;dr is that, at this point, optical viewfinders are overrated. The best EVFs are just as good.

Pros aren't married to glass or to viewfinders, though. They're married to lens mounts. Glass investment dwarfs camera body cost. That's the sticking point.