City's attack is clearly superior to United's or Chelsea's.
Utd has Lukaku, who may or may not be WC based on your definition, a 36 yo Ibra getting back in shape after a ligament injury, and who else?
Chelsea has Hazard and Morata, who missed a chunk of the season due to injuries, and who else? That high a mark for Willian and Pedro, really?
City also has better backups than useless Batshuayi. or Lingard or overrated Martial.
Same is true for midfield, and here, Liverpool is included.
I don't know how you're even comparing them.
City is the only genuinely top CL contender level EPL club frpm the last few yrs. That's due to both the squad City has AND Pep's coaching.
No other team has had a top-team level squad in EPL lately till now. One coach stepped up, did well, and took advantage of the mediocrity each season and dominated the league (for Leicester, dominated by their standards). Ranieri two years ago, Conte last season, Pep this season. Diff now is Pep also has a great squad, hence even bigger domination.