I'm not sure I agree with your thesis. For instance, Javascript has recently added an OOP class syntax, and Typescript extends the result with strict types. (JS was of course in some sense object oriented beforehand, but it wasn't recognisable to most working OO programmers as OO.) Moreover, I think you need a deliberately hamstrung language to get a genuinely OOP language - C++ and Javascript are both fully capable of writing OO code, but most people shy from calling them OO languages because they're not limited. A more interesting question is whether new programs are object oriented, and I guess the answer here remains, broadly, yes. This is why Javascript got class syntax.

But I will assume you're a better observer than me, and make the following claims:

I think there's two reasons: Object-oriented style inheritance is unsound (inheritance is not subtyping), so academics don't like it. Moreover, classical OO is not composable or extensible - unless you write your own primitives in every application and end up with Java-like verbosity. Therefore, research in new features tend not to be object oriented. Therefore, new languages tend to adopt non-OOP styles.

The other reason is probably that there's enough OOP languages. The effort it takes to create a new OOP language exceeds the effort it takes to shoehorn your OOP algorithm into an existing OOP language. Therefore, there's less motivation from the engineering side.

On the other hand, there's still lots of scope for better functional style languages; that marketplace isn't exhausted yet. Rust, for instance, merges a lot of academic techniques trialled on functional languages with a systems programming architecture.