Bigyó bácsi Azt írják, hogy az nem baj, az csak egy fedő, alatta a folyamatok futnak.
Plymouth is not slowing your boot-up process! Plymouth is responsible for the boot-up splash screen. Please read Plymouth.
It loads the boot-up logo at the beginning of the boot-up process and then waits until the boot-up process has finished so it unloads the splash screen. That is all it does and that is why it has to run in parallel and co-exist throughout the whole boot-up process. It does not delay anything, it just waits.
That is exactly what is happening. No more and no less. Please take a look at the output you added to your question and carefully read the following: