It’s a wonder anyone continues to do business with us.

Not sure what countries need with a small number of (very expensive) stealth fighters. They're not needed to enforce one's airspace or check out wayward airliners. They're too few in number to stand up to a serious invasion... Isn't this why the F-5 and F-16 and their Euro counterparts were created, so as to have a larger number of effective fighters?

Stealth can be dealt with, particularly in small countries like Switzerland, by advances in multi-frequency radar (or other spectral areas). Defensive missiles and drones are way cheaper and there's still a lot other be said filling regions of space with chunks of metal.

Nothing what you wrote makes much sense. It's like asking why buy a new MacBook for your company when an IBM/360 will do.

F-5 is a 70 year old plane that stopped being manufactured 40 years ago. F-16 was also introduced 45 years ago, predating most of computing industry.

We have learned a few things about designing planes since then which is why F-35 modernizes those designs.

Note that the f15 and f16 are still in production. It’s going to come down to the missile and support radars not the platform, and how many you can loft vs the threat.

For most applications as it were, these birds and their counterparts are fully capable.

It doesn't really change that the F-35 as an airframe is simply better across the board even if we assume equal avionics, weapons and sensors. There's just so much space in the objectively tiny F-16 for computers and there's just so much you can do with it when it comes to low radar visibility without making it something else.

Why buy a thing that's already obsolete?

(F-15s aren't really for sale or an option for most nations buying F-35.)

Isn't this the air force that unionized and doesn't work weekends so the state had to sign a deal with Italy to patrol their sovereign airspace on Saturdays and Sundays?