You and I read the same kind of stuff apparently. I have to say I haven't found any of his work to exceed his "Raise the Titanic" novel and the last ones have left me cold.
I pretty much have to agree with you. The more recent stuff with his name on them appears to have been written by a rotating committee of "ghost" or assistant writers. I won't buy anything of his that has a second author listed along with him.
I will say, though, I'm still very partial to most of his earlier work, particularly "Night Probe" and "Sahara". In fact, I even liked the movie version of "Sahara", although it left out most of the best stuff from the book ...
I read all the Dirk Pitt novels up to where he started collaborating with his son. I started one, but got diverted and never went back to it. Read a couple of the Kurt Austins but they didn’t really grab me, either. Recently I read “Golden Buddha” but found that it was impossible to keep track of the characters.
On the other hand, I’ve been enjoying his new Isaac Bell series. Although set in a different time frame, it seems to capture the flavor of the early adventures better than any of the others I’ve read.
My personal favorite has always been Night Probe, and Cussler once told me it was his favorite plot of the ones he’d written to that point. He also told me that he wanted to actually use the name James Bond, but some miscommunication led him to believe that he couldn’t. Turned out that the literary rights to the character name are held separately from the film rights, and it could have been worked out.