Who says it doesnt give him great strength? Im comparing Hybrid and Base Kaido and Hybrid is objectively a good deal stronger physically.
Read what Ginny says here, Oda seems to think Kaidos fruit is top tier.
Id say its about equal because Kaido also spent time developping his fruit given how easily he was lifting Onigashima vs Momo who was literally out of breath after pushing it for a few seconds. His Drunk Hybrid forms, his Flaming Blazing Bagua,etc.
Thats true but there is a reason people meme on the admirals so much calling them devil fruit merchants.