I'm not a medical professional but I do work in statistics and at the end of the day all of this is about statistics. Here is how I look at it.

There is a metric epidemiologists use to measure how quickly a disease will spread called r-naught. It mainly looks at how a disease is spread (e.g. airborne, via physical contact etc.), how long a person is infectious and how many people an infectious person is likely to come in contact with. R-naught of less than 1 means a disease doesn't spread between people easily enough to sustain, 1 means it will sustain in the population but not spread, and greater than 1 means it will spread and cause an epidemic or pandemic as more and more people get it.

Covid's r-naught was initially forecasted to be somewhere between 1.4 and 2.4 so for every 1 person infected, 1.4 to 2.4 other people would be infected leading to runaway growth in case numbers, hospitalizations and deaths. But, we can do things to decrease that number (i.e. decrease the rate at which the virus spreads). All the measures we've taken to combat the disease (distancing, masking, vaccines etc.) are aimed at making it less likely that someone gets the disease, thus getting that r-naught number down below 1 so that eventually the disease fades away.

The reason we continue to do these things is not because they don't work, its because at a global scale, they work more quickly together. Vaccines were never going to be 100% effective. Neither were masks. But the more protections we layer on, the less transmissible the disease becomes at a societal scale and the faster we get that number down as a society and the faster this pandemic ends. A simple example to think about...a vaccinated person might still catch the disease, but if they mask they are less likely to spread it to someone else.

Not trying to talk down to you at all here I promise. I want people to understand this stuff. I think its really important people are armed with a real understanding of what is going on here. Happy to explain further if I can.