Tuesdays can also be busy. Probably the best way to figure out crowds are two things: single day ticket pricing and Magic Key blackouts. Enchant Keys are blocked on Saturdays. Imagine Keys are blocked on Saturdays and Sundays. Believe Keys aren't blocked at all in September.
https://disneyland.disney.go.com/passes/blockout-dates/
https://www.undercovertourist.com/los-angeles/1-day-base-disneyland-ticket/
Lower tickets prices can be misleading. Do they increase the amount of people that show up because it's a cheaper cost per family or does that mean Disney thinks those days will be really slow? Higher ticket prices could lead to less people showing up.
I use Touring Plans but they can be wildly off. I mostly use it as an educated guess but I don't take it as gospel. Everything is kind of a guess now but what I've seen lately, weekends are better because the high ticket prices combined with 2 keys being blocked make the parks less busy. Sundays seem to be really good.
The best advice is to commit to doing rope drop at 8am and you can get a lot accomplished before the late morning crowds arrive around 10am to 11am.