Theories are tested and observations are made. If we’re lucky a positive result emerges, but more often what you get are results which just put constraints on t

Theories are tested and observations are made. If we’re lucky a positive result emerges, but more often what you get are results which just put constraints on the theory. For example MACHO theory was once seen as very plausible, but observations of gravitational lensing have placed strict limits on it so that it seems increasingly unlikely. Sometimes the process of constraining theory leads to a reformulation of the theory, sometimes to its abandonment. Other theories which more agreeably fit the constraints may come forward (i.e. WIMP theory on the case of DM), and they may in turn be abandoned or reformulated. That’s science working as intended, or as people here like to say, a feature and not a bug. The more a theory has to make assumptions or introduce things like new particles and fields to make predictions, the less popular it tends to be. Of course once you constrain the solution space to the point where the simplest theories can’t hold, you have to consider the more complex ones. The important thing to remember is that none of this happens in a vacuum, and while personal preferences play a role, they do so only insofar as the constraints placed on theory by observation allow for it. Incidentally that’s also why falsifiablility is such a big deal, because in its absence you can assert or believe any old thing.