Having always been fullstack even in my current large traditional bank, I see both codebases in Java 6 and maven poms that are a paradise to change (and a java 8 upgrade is often trivial and sufficient to get most of the nice candies you really need), and yarn/npm frontend projects that cant be even rebuilt two weeks later, everyone insanely writing auto updating version descriptor (^2.0.4 with the ^).
I cannot understand what idiot thought it d be fancy cutting everything into mini dependencies that update every day without you knowing made by amateurish hipsters who transitive depend on each other like their life depended on it. Yes you can lock but every build script I ve seen forgot this detail and resolve anew the dependencies !! Why !?!?
Yes it s a pain to move up a version sometimes in Java, but we decide to do it for a reason, spend a few days tops fighting it if we must and it's done. You re right that in JS I cant even teach my more backend colleagues how the fuck it works and how I can navigate it. And I m very against transpilers and linters which I try to avoid for sanity but sometimes you inherit a hero's code and you re like omfg a vue js to typescript to js hacky build chain that worked 2 years ago on bower and now bower is gone and yarn wont build it. And you re 2 weeks well into it before you start building and discussing what you actually wanted to change :D
What kills me the most is when someone in management calls the java backend that is ultra optimized, instant to change, a dream to deploy "legacy" and the yarn soup that is coded by 200 successively burnt out juniors, does 40k binding function calls on a non moving DOM (you know, to "hydrate" it with whatever framework du jour was fancy 5 months ago), and we cant redeploy without a full budget proposal, that people do everything to be assigned out of "modern" grrr
I kid you not we have an entire team in charge of one small frontent management tool for a pretrade backend, they literally spend 99% of their time justifying why they wont change it, and 1% begging me to join for a week to reorder their column or put a new button... and THEY re in charge of it argl, and I cannot for the life of me spend more than 30 minutes teaching them before they snooze "I dont get it, let s pick our battles and change that one thing with you and promised it s the last time" ...