Every chief designer, design team and manufacturer made some excellent aircraft and some duff ones and some that were complete disasters.
Some firms, like SAAB and Dassault struck it relatively lucky with a run of good designs without serious flaws.
Given the time and effort put into R&D and prototyping there really isn't much of an excuse post 1957 for designing a crap aircraft.
Pre-1945 it was always likely that imperfect materials and aerodynamic knowledge would risk a serious balls up somewhere, either excessive drag, poor handling, rubbish engine etc.
I'd give the designers of 1944-56 some leeway given that jet technology changed so rapidly and that it was hard to keep up with all the changes jumping from straight-wing centrifugal turbojets of 600mph in 1944 to delta-wing afterburning-axial flow turbojets with Mach 2 performance in 1954.
These days it takes you a decade just to mess around with CAD and CGI before you even finalise the design.
However Britain can still take the design lead and get the aircraft it wants with less compromises demanded by other partners who will stall take a good chunk of the cost burden from Britain in exchange for work-share and design input.
But nation's like West Germany and Italy had active design teams with innovative designs on the drawing boards and they were licence-building F-104Gs and had other aircraft and helicopters in production. They saw themselves as near-peers and wanted to grow their industries further. So for them obtaining maximum workshare was key.
To maintain their lead, Britain and France didn't want to give up their leading share - plus the more partners you have, the more ways the cake has to be cut.
Perhaps the greatest mystery is why countries kept/keep partnering with France. There is hardly a single collaboration that does not involve argument and bad feeling, regardless of the nation they pair with. There are multiple cases of undercutting quotes supported by government credit, attempted dumping of ex-AdlA airframes, bribery etc. in many sales contests all over the world. And yet despite all this, somehow they seem to have attracted partners and still do (SCAF etc.) despite all the aggro that comes with it. Perhaps the end product makes it worth it?
Britain lacked that post-1960.
This week at Kew I found a humorous item in a Foreign Office file; a clipping of an article in
Le Monde complaining that the British had adopted French sales techniques and were being more successful than them!!