The Higgs boson was only inferred by the mathematics, rather than observed in reality, and its existence was not proven--until it was. Dark matter is much the same. Either we will actually find some, or we'll discover something else that's responsible for the same observed effects, and adjust our understanding accordingly. Either way, science has not failed. It sounds like some people are taking issue with current science not being 100% complete and correct about everything right now, and so their response is to chuck out all current cosmological science
and replace it with something that has very little empirical underpinning and no supporting observational evidence.
To me, that