City's situation is a little different. Their squad is/was a little over the hill and they haven't refreshed and replenished it well. Somewhat like us in 17-19. Of course they have better players in the first place so the drop off wasn't as dramatic but that's the route cause. They thinned their squad but didn't really replace the players or at least what the players who left provided. They are refilling now but it's a little too little too late in terms of this season. So yes they've been affected by injuries but it's not the injuries as a root cause. It was letting Mahrez, Sterling, De Bruyne, Rodri, Jesus, Alvarez, Cancelo, Palmer, Gundogan etc leave or get old with no real replacements.
The results were better, but the results and performances weren't good before the injury crisis.