Are essentialism and historicism misdefined?
Confusion of essentialism
Karl Popper wrote that it is a fallacy, the essentialist fallacy, to ask what something really means. Insofar it refers to fixed words with unclear definitions, this may be the case. However, it is also a fallacy to assume that there cannot be any thresholds at which qualitative change takes place. For example, is it a fallacy to ask what boiling water is? The act of asking the question does not imply belief in a substance found in boiling water and only boiling water. There may be purely practical definitions based on phase transitions.
If one was to apply vulgar anti-essentialism consistently, it would condemn Karl Popper's idea that the evolution of more sophisticated language led to a threshold at which more ideas were passed on than were lost (ushering in culture) as "essentialist".
The danger of slamming quasi-essentialist language
Semantically oriented anti-essentialism that attacks anything that is formulated in quasi-essentialistic language is always in severe risk of attacking scientific argumetnation that merely happens to be verbally formulated in a pseudo-essentialist style due to lack of better words in the language. The only way to know what something actually means is by discussing with those who talk about it to sort misunderstandings based on choice of words out. This includes the requirement to consider and act on the possibility that some quasi-essentialistic sounding language may actually be of scientific content that is not based on any of the fallacies in essentialism.
Misapplied classification of historicism
Karl Popper did come up with some valid criticisms of the claim of inevitable laws of history (what he called historicism). For example, there can be claims about the future that lead to what they are claiming, such as someone claiming that a bank will collapse, people take their money out of the bank, and the bank collapses. Self-fulfilling prophecies. The opposite is also possible, for example information about the dangers of PCB leading to cuts in the pollution with PCB. Self-preventing prophecies.
This, however, is sometimes misapplied to say that any claim of a behavior leading to an inevitable consequence constitutes "historicism". For example, it have been claimed that the hypothesis that a society that uses economic growth as its primary means to fight poverty is bound to deplete natural resources constitute "historicism". However, that classification ignore the fact that there can be many societies that fight poverty by other means than eternal economic growth. This has nothing to do with totalitarianism at all.