Very crude analysis
I can see the point you are trying to make but it's different to the one I was making. I was suggesting that in games where we were leading or maybe even drawing, made subs and saw out the game for a positive result you will find little comment about the subs made. You would probably also see little mention of being negative or sitting back.
When we have dropped points for obvious reasons it gets analysed to the extreme. A scoreline surely doesn't HAVE to improve to suggest substitutions were effective? Obviously effective in all cases is subjective as it can't be proved either way what would have happened if they hadn't been made.
Similarly we can’t prove that the substitutions did actually cost us points, as this totally ignoring anything the opposition may have done with regards to subs or tactics. The only facts are the results, and I guess it probably seems worse than usual as we have given up three leads in the last 20 minutes in the past few games to end up with two points rather than nine.