@cowanon
I'll begin with the easy one, the ozone layer. The story was memory holed because the measures needed to fix the problem were already taken decades ago basically. All that was needed was for everyone to keep to the measures (which most people did, except China, which was discovered recently to have restarted using some of the CFC pollutants) and to wait for nature to take its course and "heal" itself, which as you've noted, there has indeed been progress. It's not totally repaired, not by a long shot. But the trend was indeed towards fixing itself (up until the stunt China pulled).

Regarding Mars bacteria, there were 2 false alarms actually. First was from a meteor that landed on Earth, whose origin was established as being martian, which under microscope had structures that looked a bit like fossilized microorganisms. Later it was realized that there were minerals that could form those structures by themselves under natural conditions, and scientists came to the conclusion that it was the more likely possibility. In any case, the entire thing was inconclusive at best.

The second false alarm was them sending a probe on Mars, that scoped some soil, added some heat, water and "food", and analyzed the sample for any metabolic changes. Or in other words, it analyzed whether any byproduct gases were produced that could be the result of bacteria using the "food" and water to live and multiply (similar to how life on Earth expels CO2). And initially they got a result, and had an Eureka moment. But there were 2 problems with it. First they couldn't replicate the result with other soil samples. And second, they later realized that their test itself was flawed, because certain combinations of minerals could produce a chemical reaction with similar outputs to the biological reactions they were expecting. In the end, the entire experiment was once again inconclusive.

Regarding the Air Force pilots stories, I haven't payed as close attention, and it's hard to discuss all of them in writing. The best I can recommend is to check Thunderf00t's videos on the topic. I know Thunder isn't exactly the most respected person right now because of his bad political takes, but he still did a very good job at analyzing some of that released footage.

I'm not familiar with any statements regarding alien tech from any USA official, just with the one from Israel. To be honest, it sounded like either he forgot to take his meds or he was trying to get some attention. Didn't sound too trustworthy to me. He sounded less convincing than Alex Jones. And considering he bragged about being involved with all of that, he provided suspiciously little evidence (which is to say, none at all). So yeah, nobody cared, just like nobody would care if I went outside right now with a cardboard banner with "aliens are among us" written on it.

Do aliens exist? Statistically speaking, it's almost impossible that they don't. But we also have zero tangible evidence of their existence. So it's a bit of a catch-22.