I think we can argue about the degree to which his captaincy impacted things on the field. But your own stance is not clear as you seem to indicate he has zero to little influence on things.
Of course, assessing captaincy is not a hard science, it is subjective somewhat, which is why we all are giving our opinions and trying to back them up.
In-fighting and lack of discipline were hallmarks of the 90s team. I don't see why it is hard to believe that having many changes in captaincy in a short period will not adversely affect results, which it did. When they did have a decent captain for a longer time, Wasim, the results did relatively better, they didnt lose at home and did fairly well away.
I don't think India now are worse than before, though their batting certainly is. And it's not the case that all teams have become worse or better. It depends on the period you are comparing them with.
If you compare the teams now to lets say mid-2000s, Australia, England, Sri Lanka, Pakistan, SA certainly had better teams then. WI are around the same, NZ have got better.
If you compare the teams now to mid-90s, Australia, Pakistan, WI, SA had better teams then, England and NZ are better now, SL likely better then too.
If you compare them to mid-80s, Australia, England, Sri Lanka have better teams now, Pakistan and WI were better then, NZ around the same.