If an “alternative” method worked, it would be adopted by mainstream medicine. The fact the “big medicine” rejects something that could use to justify charging you big fees suggests that these new treatments are to be looked at skeptically.
Though if an alternative is “free”, the establishment tends to ignore it. For example, Type 2 Diabetes can be prevented or cured by loss of weight (to the point the person is no longer overweight) and by significant exercise. Exercise and refraining from eating do not generate fees, making this an “alternative” to establish medicine. So in cases where the alternative involves little or no expense, it might be valid even though the medical establishment doesn’t embrace it.