Difficult to a newskool kiddos fresh out of bootcamp that can't wrap their heads around complexity, maybe.
In my experience it's the frontend frameworks that make for worse code. Callback soup is downright simple and easy-to-follow compared to some of the atrocities that React et al have wrought. Worse, they repackage old tech as "new" while completely reworking the vocabulary and paradigms, so old hats have to relearn shit they already know because some snot-nosed Facebook engineer needs another resume badge for his inevitable 18-month departure
Just because jQuery isn't "brand, new frontend framework" doesn't mean it is good or something
From my experience jQuery leads to difficult to maintain codebases relatively fast in compare to e.g Vue.