Oddly enough, the F-18 seems to have worked out operationally.
Most cracking and other such issues can be solved by beefing the airframe up a bit. Similarly capabilities can be added. Check out the growth in capability, and weight, of the later versions of F-15/16/18.
One of the worrying factors in the F-35 is the lack of growth margin both in internal space and F135 potential thrust growth without causing a thermal problem. The lack of cooling vents due to stealth requirements means the fuel is used as a heat sink and is nearing the upper limit requiring fuel to be kept for cooling at the end of the mission.
PW claim 10-20% more thrust can be achieved by incorporating ceramic blades and other ADVENT engine upgrades - but where does the heat go?