This is an organizational culture problem and needs a serious push from multiple levels of leadership to adjust. The F-35 started as an idea to actually save money by consolidating multiple missions onto one plane, which proved a terrible idea for multiple reasons and that wasn't cancelled because there would be no other option for some of the roles it should cover.
A simplistic solution would be to design weapons around common, proven components and, if possible, interchangeable ones - designing engines and weapons to have similar mount-points, avionics that can be used on multiple vehicles and be field-upgraded and build everything about as much incremental improvements as possible (yes, I know nothing will make an F-14 a stealth fighter so some big steps are needed, but if the follow-up plane could use similar engines, that'd make logistics much simpler)
And would only cost about ten trillion to prototype and agree on design specs since every three-star+ and every design team/think tank would have a thumb in the pie and design-by-committee would have to market it with the slogan "2100 or Bust!"
That's why it'd need to be pushed from top to bottom with a "unless you have something valuable to add, stick your thumbs somewhere else" message from the top.
I think the real problem here is that land warfare itself is changing too rapidly for anyone to really get on board with developing and scaling a CAS weapons platform.
I read military writers on Quora and the general sense is that it's going to be the Army and Marines that are going to form the backbone of power projection on land. The Marines are shifting their squad composition from 3 teams of four and a leader to four teams of three. One of these squad member's only job is to operate the proliferating tech tools that's becoming available to individuals.
So it's not even certain what capabilities CAS is going to need to have in the near future. Everyone's talking about loiter time, and certainly, that's really helpful, but what about the squad's soon-to-come drones? If that doesn't make the need for loiter obsolete I don't know what will.
A squad with a reconnaissance drone and portable mortars can do a hell of a lot without having to commit an aircraft. What will they need that aircraft for? Carrying weapons that the squad can't. Cue the fighter-bombers.
I can see why the Pentagon isn't chomping at the bit to spend boatloads of money on something they probably won't even need half of by the time they're done.
We must go after the New and Shiny, and it costs billions.
Kind of like a lot in our society.