constexpr is much more powerful than just generating constants (although that is one of the bigger use cases). One of the things I like is how it simplifies doing static dispatch on template types, essentially using SFINAE under the hood but in a much simpler way to read:

    if constexpr ( std::is_same_v<T, int> ) { ... }

Vs

    template <typename T, typename std::enable_if_t<...>* = 0>
    void fn( T t ) { }

Being able to generate constants using the language itself is super powerful as well (the below is a bit contrived, as std::string_view is constexpr and obsoletes this pattern):

    static constexpr std::array<char[], SIZE> strs = { ... };
    static constexpr std::array<size_t, SIZE> str_lens = calc( strs );
    // Where calc() loops over the array and calls std::strlen, all at compile time