Usually, not always
My favourite quote from the Wikipedia article: "Upon parking at the gate, the crew did another walk around inspection to narrow down the cause of the incident. The inspection revealed that the entire rudder had broken away from the tail of the aircraft."
As a pilot however I can assure you that there are some uhh, minor, safety issues associated with rudderless flight...
In some ways, yes, F-16/18s are a perfectly good replacement for the F-35. However at this point the program really has gone on far too long to be cancelled. Defense doesn't move quickly, and given that most of the US's allies are gearing up to retire their old Hornets and Vipers and eventually take on F-35s it would screw over a lot of American allies to can it.
However, it's nearly impossible to make a reliable projection of what kind of fast jet we should be procuring. Why? Because whatever we buy will be in service well into the 2030s and 2040s, and who knows what UAV technology will look like by then.
Case in point, the F-22. Great aircraft, but can't do Air-to-Ground at all. However, if you're using Predator drones as bomb trucks, maybe all you need is a bunch of F-22s to establish air superiority. In this scenario, F-35s look pretty useless. However, maybe you find yourself up against an enemy with cheap Man Portable radar homing missiles and a system to jam Predator signals. Now your F-16s & 18s are sitting ducks and your Predators are useless. F-22s can take out enemy fighters, but there's probably not any to look for anyways. In such a scenario, the F-35 suddenly looks very useful.
The fact is, fighter procurement is an extremely long-term purchase in an extremely uncertain area. Are we getting it wrong? Probably. But can we say, without a doubt, what we *should* be doing? No way. The best solution, if you have the money, is to hedge your bets with multiple systems. Otherwise, it's just a question of guessing and hoping you get it right.
IAAMP
Really? You really think that evolution is going to work differently on a different planet?
I mean, lets think about that for a moment: evolution works on the principle of competition for scarce resources. It follows principles of game theory that are pretty much universal mathematical concepts. And, lets not forget, somewhat intelligent life has evolved in a number of species on earth.
Humans, sure we cooperate when conditions are favorable, but we'll just as soon murder each other. Dolphins, also quite intelligent, follow a mating strategy of three-man gang rape. Chimpanzees engage in political assassinations.
The fact is, self-replicated organisms will replicate until resources are scarce, and scarce resources lead to zero sum, "what's bad for you is good for me" type behaviors. Any intelligent species will have instincts to take advantage of both these situations, *and* instincts to cooperate in situations where cooperation is useful. Thus, the chances of an evolved, intelligent species being 100% friendly is fairly low.
Now, it's certainly possible that an ecosystem could arise which was so interlinked that any species which preyed on another would itself become extinct. However that's a highly unstable system; the first replicator to start eating it's neighbors would flourish right until the whole system was destroyed. Certainly, it seems awfully unlikely that said ecosystem could survive long enough for intelligent life to evolve.
Remember kids, evolution's not just some fuzzy biology class concept. It's practically physics!
"Black spots have been discovered on Mars that are so dark that nothing inside can be seen. Quite possibly, the spots are entrances to deep underground caves capable of protecting Martian life, were it to exist."
With your bare hands?!?