I did an Aero Engineering Degree at a top UK university, and am mid way through my ATPLs. Although I am now studying for my ATPLs alongside a full time job - it is no walk in the park. Don’t be fooled. There are maths heavy subjects, and knowledge heavy subjects - but you need to pass all!
So although it is not necessary as per the entry criteria to be a wizz kid, when you have to calculate a flight plan under time constraints, remember Gen Nav formulae under exam conditions, if you don’t have a sound basic background in Maths - you will fail. I am surprised airlines like BA are willing to take that gamble, providing they have pride in all pilots to have ATPL results of greater than 85% overall.
That’s not to say the ATPLs are impossible. You just can’t go about them with the opinion that you’ll wing it by learning the banks. After all, who wants to board an aircraft with someone in the nose who doesn’t have a scooby.