That's because JS is not a functional language. You are enforcing a functional style by discipline. Additionally a huge portion of benefits of the functional style are lost on untyped languages. If you're not using typescript you're dealing with a lot of unnecessary bugs.
If you guys moved to a fully functional paradigm where the language enforces the functional style you will see greater benefits.
Unfortunately for the front end the ecosystem for functional languages outside of TS/JS is not that great. But an easy one to try out to actually see the benefits I recommend writing a little app with ELM. With something like ELM, the functional style is enforced by the compiler. You will see that 90% of the bugs you typically deal with in JS/TS will disappear. One type of bug that will disappear is runtime errors. Runtime errors are not possible in ELM.
I find a lot of JS programmers haven't fully grokked the functional style. Example: You'll find JS programmers who talk about how much they like functional programming but don't understand why for loops don't exist in functional programming.
If you guys moved to a fully functional paradigm where the language enforces the functional style you will see greater benefits.
Unfortunately for the front end the ecosystem for functional languages outside of TS/JS is not that great. But an easy one to try out to actually see the benefits I recommend writing a little app with ELM. With something like ELM, the functional style is enforced by the compiler. You will see that 90% of the bugs you typically deal with in JS/TS will disappear. One type of bug that will disappear is runtime errors. Runtime errors are not possible in ELM.
I find a lot of JS programmers haven't fully grokked the functional style. Example: You'll find JS programmers who talk about how much they like functional programming but don't understand why for loops don't exist in functional programming.