True. However, that’s what you can expect with an autocratic system with no rational method of succession.
This absence of a coherent method of determining the legitimate succession continued throughout the entire Roman and Byzantine periods and was, IMO, the single greatest factor in their decline and fall.
Even the western European primogeniture system was preferable to the half-assed inheritance crossed with coup system of the Romans.
The Roman Empire was dysfunctional at the top, but the beast still survived a long time. Had Rome not had that resilence, it would have disintegrated by the time of Nero [if not Caligula.] Or, it would have disintegrated under a later reformist like the U.S.S.R. fell apart.
Instead, the Roman Empire lasted five centuries - in the West; the Byzantine empire carried through for about nine hundred more years. Given that incoherence you mentioned, it's amazing it survived that long.