I think bringing new players to Manchester City is not the main solution, not unimportant, it's just that it can't be a priority, Manchester City already has talented and even expensive players, Manchester City has a lot of potential players, if they are really utilised they can win the remaining matches, It's easy to say but it doesn't mean it's impossible, and the Coach needs to review the strategy on the pitch, if necessary try the players on the bench to play at the start of the game.
I understand where you're coming from, but things are a bit more complex than just looking at the current squad and evaluating the talent of each player.
Something is clearly not working with the current team and it's possible that it's due to some psychological factors or problems with morale. Sometimes a change is needed just for the sake of it. Bringing in some fresh blood, even just 1 or 2 new players could work wonders, as they could bring in some fresh motivation and won't be carrying that mental ballast the current players are.
So just because the current squad could deliver great results in the past years doesn't mean that will be true forever. Professional football is a fast-changing environment. What worked fine yesterday, might not work today.
What you say is true, well, let's see in the January transfer window, whether there will be good players who can bring Manchester City to be better, giving a glimmer of hope to bring out of the current slump.