I am not a scientist and certainly not a pharmacologist. I have no idea what mechanisms Ivermectin proponents propose or the double-blind studies I have seen indicate that it doesn’t work (so there probably isn’t a real mechanism).
However, your argument is profoundly unscientific. The idea of science as a different field of study from philosophy is that it starts with observation and only then looks for the mechanisms to explain that observation.
For example, Newton observed gravity by seeing things fall and the movement of the planets and realizing that mathematically they could be calculated the same way. But Newton did not have any explanation of how objects attracted each other. (Indeed the mechanism of gravity is controversial to this day) It did not matter, however, because he, and we, can consistently observe gravity happening.
This has been the case with many medications as well. The proposed mechanism is only arrived at after the medication is observed to work. For example Penicillin was discovered and used as an antibiotic for years before a theory of its mechanism was proposed.
Ivermectin doesn’t work. But if studies had shown that it did, its mechanism could be worked out later.