I haven't kept up on the F-35 lately. But this is a jet made of compromises. The Pentagon knew they couldn't get funding for multiple new jets. The F-35 is trying to do to much by being a jet for the Air Force, Navy and Marines. So they combined all the requirements for the specification. Combining the requirements of the Air Force and Navy probably isn't so bad. The Marines requirement of the F-35 being VTOL capable is holding the design back. I accept that VTOL is a key requirement for the Marines, but the F-35 has made a lot of trade offs for that feature. While I don't know how successful the F-35 would be without VTOL, it has to be better then what is being delivered.
Most of what you wrote is wrong. There are three versions, the F-35A, F-35B and F-35C for the AF, Marines and Navy respectively. The three split a long time ago, so no version is holding any other back.
Where things aren't so good is that the three versions were originally supposed to have over 80% parts commonality. That is now down to something like 20%. That is bad in terms of economies of scale.
All that said, in principle there is absolutely nothing preventing a single, mostly common, design from filling those three roles. Whether the F-35 team has done an exemplary job of doing that is certainly a question.
In terms of sheer engineering, it can be argued that the F-35B is the most impressive of the three versions. It's the first supersonic VTOL fighter ever.
From a Bloomberg article* yesterday:
"The lift fan made the common fuselage bulkier than it otherwise would have been. That, in turn, increased drag and decreased fuel efficiency and range."
This quote from the article reinforces my view that the VTOL requirement does effect the other version of the F-35.
