Sometimes I feel this way too, most of the competitions don't interest me much.
One benefit that does happen is it spurs mass public transit expansion (Peertube version) big time in the host city. The sheer volume of athletes and visitors to one area means that your usual 1 hour or more commutes on already congested roads aren't going to cut it.
This event makes a city/country get off their ass, stop being complacent. It makes a convincing case for deficit spending to meet public infrastructure needs, which are so often neglected when left alone.
It makes the public go into massive debt for the benefit of corporations who make bank. It leaves the city with a dozen world-class sports venues that will never ever be used to their capacity again and which the host city will be unable to maintain, but which they paid for with public money.
What you're saying is true, there is definitely corruption, useless building and parking and unequal wealth transfer that happens with the Games in its host cities.
However, my point is that there is a subset of that built infrastructure that does eventually see its capacity realized again, and that's mass public transit. It's easy to see the value of that infrastructure in hindsight, but many politicians and residents are skiddish about making the short and long term investments needed to provide transportation services and meet future movement needs of a population. The Olympics provide a guarantee that the infrastructure will be used even for just a few weeks, which help quell fears that the transit spending would be wasted money. Seeing that we still benefit from transit infrastructure built for that short event, should make people see that transit investment is valuable for all of us.