[kypro]

You're not alone - it's nuts how much JS has changed over the last decade.

I don't know if I can offer any suggestions beyond just Googling syntax you don't understand and experimenting with it until you feel you understand it. From there it just a matter of time before you can glance your eye over the code and understand what it's doing without needing to decipher every line. I just want to say you're not alone. I think most frontend devs have gone through something similar at some point over the last decade - I know I have.

As for deprecated dependencies, that's a huge problem. Senior devs generally do care and will be selective around dependencies. One of the problems is that the ecosystem is evolving so quickly. Libraries come into and out of fashion almost over night so frequent maintenance is needed to keep dependencies up to date. My guess is that either devs are not putting enough thought into what dependencies they're using, or your not currently assigning enough time as a team to review & maintain your existing dependencies - this is definitely something worth raising with your team imo.

The last thing I'll say is that the use of ternary operators are something I'm very critical of and it's interesting that you mentioned them in your post. A lot of devs seem to have this mindset that if you can convert 5 lines of code to 1 or 2 that's always a good thing, but compressing 5 lines of code to 2 often comes at the cost of clarity and readability. It sounds like you might need to think about coding standards with your team. Is part of the problem here that the team is writing confusing / messy code, and it's that coupled with your lack of knowledge of modern JS that's resulting in the stress you're feeling here?