Bacteria works symbiotically which is why the research suggests taking multi-strain is better than taking high doses of one particular strain. You also have to take into account the quality and shelf life of the probiotic and the duration it is taken. What you can't deny is that the Science proves there is direct correlation between gut microbiome diversity and disease.
I experimented with ibbns specific brand 'Nature's Pearl' and I noticed no change but there could have been many reasons for this. Like you I was put off probiotics, but only for a time. A lab test I had showed my microbiome diversity in the lowest quintile.