Surely this must be a parody post. Well done.
Let us suppose that Bruno misses 10 pks straight, all having gone well above the crossbar. Would it be a matter of mere opinion that Bruno’s performance in taking pk’s over those 10 missed pk’s was poor?
Before you answer that question, what you’re missing is that adjectives like the word “poor” can be factually true descriptions of the noun they are describing. On the example above facts not only conclusively support the factual statement that Bruno’s last 10 pk’s were poor, there can be no plausible counterclaim that his 10 pk’s were well taken and that he was the victim of bad luck such as wind gusts.
When assessing Rashford’s performance before his turn for the worse over the last year, it was a factually true statement that he was playing well. You can use other adjectives such as “brilliantly” and the like, but the truth of the description was backed up by various performance metrics relevant to his position. It was not a mere opinion, as valid as any other mere opinion, that for a time Rashford played well, or brilliantly, for United. It was fact.
A QUINTESSENTIAL opinion would be something like whether blue is a more beautiful color than green, whether United’s zebra away kit last year was gorgeous (I actually know a United supporter who loves it), or whether broccoli tastes great or terrible.
In the interest of brevity I’ll leave it there but there is much more to be said to explain the difference between provably true characterization of past events and characterizations that are subject to reasonable disagreement. No reasonable observer would not, for example, in any way deny that United were playing poorly under Ole in his last two months as manager. One could make the argument that despite being outplayed badly match after match that we were playing brilliantly under Ole during the Liverpool, City, Watford and other matches, but the overwhelming weight of the evidence would conclusively disprove such a claim.