Codeigniter simplicity and easy of use because they offer simple solution to solve common problem. CI4 is completely rewritten and adapted more php functionality. If dev team could write a better code and organized it well, i'm sure the usage will be simple and not too complex. The code itself might be to complex, but hope not the usage. How many of us use frameworks but it does not enforce us to know how it really works(just read docs). Don't worry, dev team is good, they will not burden us to undestand how they do their jobs.
Keep calm.
