The last company I worked for it honestly took me about two months to actually grok what they were doing with their forms because I couldn't fathom why you'd do this input-listener business on the FE while the backend was all Django APIs. They had re-engineered a form wizard flow and scattered the state management into three places (some in the API calls, some in third party API calls in the middle of the flow, and a decent chunk in the React flow via cookies/sessions). It was madness trying to debug it.