A range of theories that are properly counted as scientific cannot be falsified at present and quite possibly never (eg Hugh Everett's Many Worlds Interpretation).
Although it seems to get loosely refered to as such, Hugh Everett's Many Worlds Interpretation and its many offshoots and rivals don't fit any criteria for being called theories. Hypotheses at best, conjectiure maybe but speculation would be nearer the mark. A quick peruse of the internet suggests that nobody has much idea what he was on about.
However what can be done is to seek alternative explanations which deal with the anomalies involved more satisfactorily.
WOOZLES!
If this can be done the credibility of the theories involved are reduced, if it cannot be done, the credibility is strengthened. That involves critical analysis.
All the necessary critical analysis has been done. Did you look at those links I gave you? It's tosh and fraudulent tosh at that.
The suggestion that critical analysis which reduces the credibility of a fallacious theory at the same time gives it greater credibility is hard to sustain.
As long as they are being talked about, they are still in the game and are happy. Don't feed the troll.