As the intro page demonstrates, modern C++ isn't really all that messy. I think there's a solid argument that it's a more dependable option than Dart, which isn't really used by anyone other than Google.

Better languages have moved beyond C++. I've developed software for over 20 years. I've use C++ for many of those years. Software languages and tools have evolved past C++.

Imagine the "evolution of man" drawing. C++ is the middle guy not exactly standing upright.

An "evolution of man" drawing wouldn't really be accurate because it implies each entry is static in terms of evolution. C++ is very obviously not, and modern C++ is barely recognizable compared to code written years ago.

While I really like Flutter, there should be alternatives for everyone, and that includes people who doesn't like Flutter.

I agree. All should choose their own languages and tools. The more competition in the marketplace the better. Hopefully the one you choose will have long term support, be accepted by industry and developers, deliver on the promised marketing, and have reasonable open source licenses. Anything else?

Any recommendations on good sources for tutorials? Just the flutter dev channel or are there any good 3rd parties?

performance. the Dart VM is one thing. C and C++ are closer to the bare metal.

Only debug builds use the Dart VM -- release builds are native code. If you want to execute C++ you can do so via native channels.