The difference is that you're dismissing the entire field of mainstream software development for the last couple of decades as “elementary school” level abstractions which “do a very poor job of solving more problems than they create”. A strong majority of working programmers are familiar with those concepts because they were taught those concepts in schools, by industry experts, and see them used by platform developers and vendors.

FP is not that pervasive and anyone trying to make the case that it's better across the board has to address that familiarity gap. Try to think about, say, the average Java or C# developer working on a large project. They aren't spending their day saying “OOP is terrible” and when you say something is better because it's “grounded in mathematical practice” that's really non-obvious to someone who's thinking the main way their life would improve would be if they could get the business stakeholder to make a decision and stick with it for more than 24 hours, stop using Oracle products, etc. Talking about avoiding shared state and side-effects, going beyond Java-level typing to make refactoring safer, etc. is a lot more useful since those probably are things they spend time on regularly.