Earlier quoted context omitted.
This is absolutely the situation I am in right now, and I desperately need all the guidance I can get. We’re talking thousands of lines of React components that rely regularly on manipulating global js variables, mixed with MVC 5 written in Razor delivering variables in script tags, mixed with outdated jQuery, that’s all just concat’d together with gulp and that hasn’t seen a refactor in years of changing hands with…
Personally I thrive in this kind of environment, it's a kind of comfortable chaos. MVC5 is positively modern compared to many of the products I've worked with which have included (within the last 5 years) VB6 winforms but mostly aspx webforms. Understand that previous developers might not know what a DOM is have likely written ad-hoc jquery snippets, included 3 different versions of jquery-ui until they happened acro…
Also worth considering that some people never learned how to handle constructive criticism and will take any suggestions as personal attacks. Stay as far away from these people as possible, you aren't going to change them but their pettiness can make your life miserable, particularly if they're closer to management than you are.