I have a slightly different idea, Haaland is not the key factor that helped Man City win the championship. Erling Haaland is a small player in a big match, he always fails in the final.
EPL is tough because the elite and average club are competitive. Manchester City won the EPL title because Erling Haaland made good use of his goal scoring opportunities and also his teammates played a major role in game victories. Pep Guardiola arrange his strategy and every player played a role in accomplishing their targets, no one was left out. Erling Haaland is a top player and goal machine for Manchester City. 
Of course, if PL is still highly competitive consideirng it's a league with the biggest income. Refer to the revenue comparison with another league, PL is still leading the way as a league with the highest revenue. Though this information was collected a few years ago, we might speculate that revenue may have increased by 10% to 20% since then. The league with the highest income is still the PL and this is helping the club to buy expensive players that makes the competition even tougher.
Certainly, if the top club was always blowing a lot of money to win the league. You will get rich if you win the EPL. To strengthen their team, clubs are therefore spending a lot of money on players. In football, this is customary.
EPL is hence highly competitive. The only issue is that, like Manchester City, the priciest team in the league still rules. Just so you know, this club has the most income among the cities.