The pthread extension has stopped updating and cannot be used on php7.4. In order to run on newer PHP, what will Pocketmine use instead of pthread? https://github.com/krakjoe/parallel? https://github.com/amphp/parallel? Or even multiple processes?
I have no plans to move away from pthreads at present, and there's also no significant appeal to 7.4. I have a fork of pthreads which runs on 7.4, but it's unstable and still needs work.