some problems are better solved via OOP, others through functional programming. The perfect language would be a successful blend of the two.
That was the entire goal of Scala and I would say Scala both accomplished it and is a worse language for doing so. Some OOP principles are just bad, namely subtyping. Rust genuinely does blend OOP and Functional in a better way. Instead of classes and interfaces with lambdas you have algebraic data types and type classes with for loops.
You just change it when you want to drop any profile you developed. ie on browser start. The problem with changing it every page is sites will assume you're a bot and either block you or serve you a captcha on every page.