I’d like to know also. You say you are not a historicist, if you say the first seal (first horseman of the apocalypse) is the end time antichrist going forth with war, famine, pestilence in his wake (the other horsemen), then, indeed you are not a historicist. However, if you interpret the first horseman as some figure of history, Nero, one of the emperors of imperial Rome, or Papal Rome, Mussolini, etc., then you are historicist plain and simple.
If you would just tell us who you interpret the first horseman to be, it would settle the issue.
The horseman cannot be antichrist, he comes after the seals.
The first horseman is the chain of human governments setting out to conquer the people and their rights through their “Mystery Babylon” cliques.
Part of Revelation has to be past, and part has to be future to satisfy Yeshua’s commission to John.