That means Musketeers, Guardians and Gifters are not that impressive.
That's a very weak reasoning.
Instead of admitting that Jack is simply that powerful, you downplay the Sulong Musketeers and Guardians instead?
It is a known fact that their Sulong mode make them significantly stronger. It is definitely a major PU.
We have seen how fullzoan form Jack performed against Inuarashi and Nekomamushi and even in his full zoan form he couldn't take either of them down in 1 day.
And? Even then, Jack was fighting against the entire mink tribe, Inu and Neko were switching each 12 hours to rest a bit before they fought Jack again.
Furthermore, if hybrid Jack starts overpowering Sulong Inu/Neko, your argument would be invalid anyway since it'd be clear that Jack didn't even use his hybrid against them back then.