It may be correct that nobody has immunity against the virus. But there are instances where people did not get the infection even having close contact with the patient. I know two people who travelled with infected patients without knowing they had covid and later went to quarantine but we're not infected. Either these patients may have good immunity or the virus may have got genetic transformation .i believed that way.
Were these people TESTED and confirmed with a NEGATIVE outcome ? Otherwise if no testing occurred, they could have very well been infected but remained asymptomatic or very mild symptoms and just "rode it off" - OR it could be some amazing coincidence where even though they were in proximity to infected patients, were NOT exposed to a big enough "viral charge", if any at all. Being near a covid19 person does not guarantee you will get infected, you may in theory even touch a patient and get the virus on your hands and never get infected. The virus needs an entry point, so in theory if you wash your hands, avoid touching your face or any area of your body where the virus can enter, then you are safe, and if you somehow manage to not be in contact with a person's droplets (common carrier of the virus) then you won't get infected. The most common spread is through coughing, breathing, sneezing, through droplets that enter your airways. How close were they to the patients ? Were they wearing masks ? Were the patients coughing, sneezing ? Were the those two people ever in contact with the patient's droplets. You don't just get infected with COVID19 by being with someone infected - unless there is a channel where the virus can travel. Maybe the viral charge was not enough to get them infected, maybe they were infected but did not develop complications, as allegedly most people, but otherwise full immunity, assuming the virus entered those 2 and got immediately neutralised by antibodies, I do not believe so.
Your second theory however, I agree with, the virus may have transformed into something that is more virulent and contagious, that's what viruses do, mutate, though hopefully covid19's mutation is slow, and HOPEFULLY if there is a second wave, it will be short lived, and hopefully eventually the virus will be less strong until eventually vanishes, can we be so sure ?
Yes some people have amazing genetics and immune system - some people can be infected and never know it, because their body's immune response was quick and did the job, whilst for others, their body's immune system went into cytokine storm and ravaged organs, until eventual death.
NOW let's assume your first theory is correct, mysterious immunity to viruses, that would likely account for a tiny percentage of the population - It would be an extremely dangerous assumption to make for people not to follow rules, just because they heard that some people are allegedly immune and will never get the virus even when exposed. Yes many people do not get infected despite being exposed to positive patients or people, BUT in parallel, MANY DO.
You can never take chances.
I have read of cases where people get infected even when applying distance, wearing masks, and wearing all the protections, visors, etc.
If we talk *FACTS*, the pandemic is far from over, there WILL be more deaths, far more deaths, far more cases, spread, and a second wave WILL happen, as history shows with viruses....other than that, nobody knows how bad things will be and how long this will last But if selfish people continue defying rules to prevent spread, for sure the situation will be catastrophic and send this world into a great depression.
China's stance on Hong Kong is not helping, adding more insult in the middle of a pandemic and potentially sending Western world into a full blown recession / depression post pandemic.