So by your own assessment the 50 1.4 and the 50 1.8 STM are incredibly similar image quality wise. At a fraction of the cost of the 50 1.4, how does that not put the 50 1.8 STM miles ahead?
Firstly, value for money hasn't been cited by anyone criticising the 1.4, to my knowledge - they've just criticised the 1.4 outright as effectively "not much good".
Secondly, they may be similar in terms of image quality but the 1.4 is half a stop faster.
I don't dispute the STM is better value for money but to say the 1.4 is inferior in absolute terms isn't fair.