I disagree.
That can be valid only for people that play this game as a job and not for everyone or most people. There is always higher difficulties you can get into for who want even more challenge from the get go, but for the initial fases of the game it’s very unusual to say the least that more often I feel depowered when I level up, instead of stronger. And since your loot is very much luck based, it can take a while until I find the good loot replacement to put me back on track. So having different zone with little level differences bellow the players (just like those above your level you have in the begining) should be a fair compromise.