Marines not Navy, though they're a sub org of the Navy so a reasonable thing to say.
There's a Rand study on it. They concluded that the attempts at commonality didn't just fail, they proved counterproductive. They did a historical review of joint acquisition programs and found basically all of them hit the same flaw. As appealing as it may seem to congress, it's a bad strategy.
The F-35's problems as far as budget and schedule slippage were largely in the software section, and a lot of that goes back to structuring it as a single source cost plus contract. That incentivized LM to make the project as big and delayed as possible.
LM is infamous for this sort of thing. They turned Aegis into a clown circus of a billion different ship specific variants where they could charge N times to fix the same flaw in different nearly identical codebases. The Navy has been trying to extract themselves from it for like 2 decades now, with some signs of success finally showing up.
In short, LM is behaving in bad faith. This is unsurprising. They basically invented these tactics some decades back.
Back when Ash Carter was Sec Def, he called in LM and demanded they start hitting the promised numbers on marginal airframe costs. Reportedly the conversation went something like "do this or we'll curtail our buy" to which LM responded "by how much?" As replied "how about none?"
Suddenly they started hitting the numbers, surprise surprise.
We're about to have the same conversation about sustainment costs. I hope Austin drives as hard a bargain.
If you've read any of the limited info coming out about some of the AF's new projects like the B-21 or NGAD, it's pretty clear they took the lessons from the F-35 to heart and are using a very different approach, one where they hold the reigns of integration and can create competition at any time.