Oh boy, here we go (inhales):
Agile isn't that bad. People just believe they are more productive if they are "heads down" and not held accountable for what they write/do.
Functional programming isn't that great and doesn't solve all of the world's problems; it just pushes the issues with state to other parts of your design, and doesn't scale well in deeply nested solutions.
IDEs with proper code support (i.e. automatic structure analysis, autocomplete, etc.) are one of the best ways to deal with a large codebase that needs refactoring. Doing widescale refactors without one is asking for trouble. If you believe you don't need it, either your codebase is just that small (which is fine) or playing with fire.
Much of the advice out there on architecture and tooling isn't properly contextualized on the codebase, market, and team situation. If you believe you have the One True Architecture Solution, you are naive. (Ex. Microservices, large complex code pipelines, monorepos, etc.) Be especially wary of anything from FAANG engineering blogs unless you are also in another letter of FAANG.
There. Got it out of my system. Have fun dissecting it.