Disney wants it this way and they explicitly stated it during the Chapek era and on past quarterly performance calls. I am not here to get in an argument with anyone, nor am I saying I agree with the thinking, but Disney states that the summer tourists visiting the parks spend more money than locals. Out of town visitors stay in hotels longer, buy more food, merch, LLMP, LLSP, etc. Even though there's less people in the parks, the people who are there spend more money and it's more lucrative to Disney. Also, the lower crowds provide a better experience for the people visiting, making them tell their friends how great it was and travel back again. This is for DL, not WDW, which is different demographics.
Again, I am not commenting on the merits of this, but this is directly what the design of the system is. Disneyland KNOWS the summer is less crowded and has been for years. They intentionally continue to price the summer at high levels and offer promotions like the 70th deal this year and the 3 day ticket deal last summer.
I personally hope they keep things this way. Summer is so pleasant to visit with long hours, max entertainment, and manageable crowds.
I also think all of us lose sight of something important related to crowd levels. Disneyland keeps ADDING attractions without removing old stuff. They've added MMRR, ROTR, MFSR. This is substantial additional capacity for people to do stuff, making waits on other rides less long. Not saying this is the sole reason for lower waits, but it is certainly at least a factor when comparing to pre-2019. DCA has longer waits consistently than DL, because a lot of people buy 1 park tickets and there's much less to do in that park than DL.
