Most people also don't care about climate change and haven't changed their behaviour as the issue became more serious and apparent, but that doesn't mean it's not a real or serious issue. Most people are simply not very informed or caring.
I suggest you don't follow what "most people" do on any matter, and instead look at the rational evidence. Covid is more damaging to organs and the immune system than the flu, and more likely to cause long-term symptoms (1 in 9 infected experience some form of prolonged symptoms, according to a recent survey by Canada's equivalent of ONS). Healthy adults only get the flu about twice per decade, according to a study by Imperial College, and usually in winter, whereas Covid is year-long and most people have had it multiple times in a couple years. It is also much more contagious, as unlike flu it is mostly airborne-transmitted. The results of unmitigated spread are already seen: record numbers of the UK workforce are out with long-term sickness. There are also increasing numbers of excess deaths with things like cardiovascular disease, especially in the over 50s-under 65s who can no longer get vaccines in the UK, and the British Heart Foundation says Covid is a factor in this.
It's also not true that health authorities worldwide have stopped advising isolation, testing, masks etc. These are still recommended guidance, it's just that it's not mandated by governments anymore. Do you only do things that you are forced to do in life? Washing your hands after using the loo is not mandated by the government, but presumably you do it...right?
It's understandable that people declared the problem "over", because as a species we can't focus on scary things for a long time without experiencing mental distress, but viruses don't care about our feelings.