That's not how 6th gen fighter combats work. You get hit by missiles and explode without ever even detecting the opponent.
Does china have better stuff than f16s? Sure (and modern f16s are not the same as 1970s f16s which makes my point harder to understand in the first place anyways) but at some point, with some military technologies, you can't beat them with quantity.
Lower frequency RADAR will pick up F-35s, but not with enough precision to generate a target track. Pilots spend a lot of thought on the problem of signature management.
A Chinese Wedgetail would be extremely dangerous, as it could provide a very good detection, and with a close enough X-band RADAR you will get a target, and then it is up to kinetic escape/EW/decoys. That is a bad situation to be in during a large force engagement.
The PLAAF is of course working on longer range and faster AEW&C and jam resistant data link and expendable sensors. It is just a matter of time.
There's a lot of things that complicate actual fights, people get lucky, people get unlucky, you do clever things like predict incoming sortie directions and saturate that area, but while the f35 is not produced in the same numbers as say, the p51, it's not "the last starfighter" either, the opponent has to get lucky a whole bunch of times before their ability to resist has been removed.
S400 works just fine for detecting F-35s.
They don't seem to have fared all that well against US/Israeli F-35s in Iran, and seem to struggle in Ukraine against far less sophisticated opponents.
Yes, that's the recurring theme in modern warfare. Cheap mass produced shit makes sophisticated tech struggle. The US is now going to be immune from this, especially since we have stopped mass producing anything for thirty years.
Ukraine used cheap drones to destroy a few S400 setups.
I can't comment on how accurate that is, but as for "cheap mass produced shit", I refer you to both times the US invaded iraq. Kill ratios on the order of literally 100 to 1. This is the point at which you can't actually overwhelm better technology with quantity.
Wars are, of course, incredibly more complicated than just measuring kill ratios and highscores as if it were a video game. There's usually multiple factions involved, all with differing objectives and those factions and objectives can change and mutate during the course of the war anyways.
If we look at a war the US unequivocally lost, defending south vietnam from the north vietnam invasion, there are a whole bunch of factors but exactly none of them involved some kind of "high tech too advanced" weapon system being defeated by "lower tech but more mass produced" systems.
Doing some incredibly basic research shows that the actual dollar cost of the vietnam war was, relative to the american economy and so on, pretty small, and not a major factor in the ultimate result of the war. Producing fighter jets or whatever that were 10% cheaper doesn't seem like it would have made much of a difference.
This actually kind of proves my point, we can "go to war" with iraq or iran and as long as we're not implementing literal conscription, the US is willing to maintain those wars for a very long time. There's a gigantic difference in public response between "2 pilots died when f35s were ambushed" and "10,000 american soldiers died in this month's battles around Baghdad". One of those gets you some headlines and a few protests, the other gets you voted out of office.
The S-300 systems in Iran were completely ineffective against IDF F-35s. Doubtful they even got a detection.
That's convenient. Hopefully they don't use their massive numerical advantage in some sort of scheme to make it not true.