and even std::map, std::unordered_map, even std::vector (!) suck

It's really hard to take your comment serious because of generalization like this. Maybe they're not usable for your particular usecase but that doesn't mean they suck. Just like there's a 'million' ways that C++ sucks in your book, there's a reason there's millions of lines of code out there where these containers are valid usecases and hence work without issues whatsoever nor a need to replace them with something else.

std::map and std::unordered_map are just unbelievably shitty implementations. The former is a red-black tree, which in my entire programming career I have needed to reach for like... twice? It's just not the right container for almost any problem you have, yet it's the one that gets the short, sweet name. The latter is a bucket-based hashmap, which is about the worst kind of hashmap that can be built. On top of that, their APIs are also really annoying to use compared to, say, Python or Rust's implementation. At least C++20 finally added a simple contains method, but something like setdefault is just a chore to get implemented.

They're not useable for anything serious, i.e. high throughput, low frequency, massively concurrent work. In other words, most of the things for which you shouldn't better have chosen a different language in the first place.

They're also unusable by the way because of ergonomic and software architecture factors, such as bad modularity, terrible compile times, unreadable error messages, unreadable symbol names...

Yes that is overgeneralizing a little bit but it's largely true.

The problem is typically not the containers themselves but all the other bad decisions that they push you to make in order to work around their "small issues".

The huge problem is that these containers can get you started quickly, i.e. leetcode type stuff and single threaded stuff, but at some point you'll realize your architecture ended up completely in the wrong place because of that.

If you haven't been thinking deeply about memory management and concurrency, you won't be able to understand, no offense meant. I've just fixed another subsystem that was completely overwhelmed, seeing 8x bandwidth gains already on a small testsystem, but the factor is basically unbounded when moving to bigger systems, when it's about contended vs uncontended.