I agree with you that Manchester City is playing weaker football compared to the one they played last season. Last season, Manchester City's performance was amazing, and they scored a lot of goals against their opponents, which helped them win the Premier League trophy last season. Since Manchester City is struggling to score enough goals against their opponent, that doesn't mean that Liverpool has a higher chance of winning the league, because if Manchester City fails to overtake Liverpool in the league table, Arsenal will do that.
We can't outrightly put out Manchester city performance this season even if it appears weaker than that which they had last season but then they have aswell been able to reduce the amount of loss they suffer as it's very minimal and not much that will look like they aren't performing well enough. Last season they has a very tremendous performance especially with the fact that the came from behind and won the League title even after winning others aswell but this season they aren't really showing such capacity but they aren't worse either, they are even showing potential in every sides which includes both in the champions and premier league so I'm very optimistic in the fact that Manchester city may get something by the end of this season.
Liverpool was able to get to the top of the table early enough and not only did they get to the top, they have so far maintained it that it's gradually beginning to look like they have got their fate sealed in the fact that they are most definitely going to be the winners of the league title after having a title to their name this season already.