Pics are 100% centre crops
"when wide open, a little soft in the middle"...I wouldn’t call this a little soft, probably "festival of spherical aberration" is more appropriate
View attachment 226734
"By f/2, the middle was sharp and mid-frame was getting much better"...I'd say definitely not sharp by any means (it's at f1.8 but you're not doing magic with 1/3rd stop extra closure), it's still partying at the spherical aberration festival, albeit it's getting close to the end of the festival...probably it doesn't catch up with the RF 50 1.8 until f5.6 or even f8 looking at the progression, shame on me I have deleted the original test pictures with the narrower apertures, so we could also look in the corners, I reckon maybe corner sharpness at f8 can match the RF at f1.8 in the centre...
View attachment 226735
C'mon, why defend one of the worst lenses that Canon ever made? It's terrible, any of the various old EF 50 1.8 was WAY sharper than this up to f4 and when you get there to match, what's the reason to buy the f1.4 if it's unusable before closing 3 stops?