It's not that Manchester City have stopped being consistent or weakened at all, no, it's not that. It's very different this year, other teams as you have already pointed out are also strong and can compete with MC. Let's see what happens in the Champions League, I think it will be a big indicator, if they reach the final or win the trophy at all, it will mean just that they are still strong, and it will also emphasise once again that this EPL season is not like the last ones.
The opponent that Manchester City will face in the next match is Arsenal and the three big clubs are competing to win and reach first place. I am sure that Arsenal and Manchester City will use all their strength with the aim of winning and will not let the result end in a draw.