"But it’s (F35) a pretty good plane"
I've never flown one, but I do provide support for the maintenance effort (Navy and Marine Corps). The pilots (most flew in Iraq and Afghanistan) really like it.
The maintenance effort for F-18 is getting much more difficult because the planes have greatly exceeded their life span and parts are getting extremely difficult to acquire. Additionally, the testing equipment was considered obsolete years ago, so getting parts for that equipment has become its own effort.
Think of it this way, International Harvester trucks were considered bullet proof, but when you spend half your day trying to find a rebuilt starter, maybe you need to move on.