John Kennedy oversaw the Hoops fourth derby defeat of the season as interim manager and Commons believes things have deteriorated further since Neil Lennon left the dug-out in February.
His departure has failed to halt Celtic’s slide and the club will endure their first trophyless season since 2009-10, and Commons says the defeat showed how far they have slipped in two months - and in the last three years since Steven Gerrard took over at Ibrox.
Writing in his Daily Mail column, the 12-times capped Scottish international said: “Just over three years ago, Celtic travelled to Ibrox and went down to ten men when Jozo Simunovic was sent off for an elbow on Alfredo Morelos.
"Despite being a man down, Celtic went on to win 3-2. They were a supremely well-coached team bursting with talent, confidence and, most importantly, pride in the jersey.
"This current team is nowhere near that sort of level. It's now well over two months since Neil Lennon left the club and things haven't improved in the slightest.
"In all honesty, they're actually even worse now than what they were a few months ago. The slide has continued unabated and they are now in one almighty mess."
Celtic fell behind to Kemar Roofe's opening goal and immediately responded through Odsonne Edouard. However Alfredo Morelos fired the home side ahead and second half goals from Roofe and Jermain Defoe capped off a miserable afternoon for Celtic, who also had Callum McGregor red carded in the first half for two bookable offences.
Commons added: "This was billed as a chance for Celtic to salvage a little bit of pride at the end of a painful, fractured season.
"Celtic went out with a whimper, unable to rouse themselves and show the levels of passion, fight and commitment that the badge on the jersey demands of them.
"As soon as Callum McGregor was sent off yesterday, you knew exactly what was going to happen. There was a sense of inevitability to it all.”