I haven't been using Codeigniter for a while. But I had a look at the website recently and I think with the release of Codeigniter 4, it is still a good choice for some.
I think for building PHP application that you sell, like scripts, and you are not sure where and how it might be installed, then perhaps this is a good option. Or perhaps building an admin dashboard for your Raspberry Pi IoT project. And I think it can perform well in big and complex systems as well.
I might consider this for my next project.
What do you think?