The shot works a bit less well against Delta, but did not in any way cause it. It still works very well for keeping you out of the hospital or the morgue.

Vaccinated people are less likely to be infected, less likely to get symptoms, and clear the virus quicker so even if peak viral load is the same they are still less likely to pass it on in general.

The necessity for boosters for healthy people with good immune systems is by no means settled science. Some people def. need boosters and we probably all will eventually. But for right now, getting the existing shot results in you being MANY times less likely to end up in the hospital and for that reason alone you should get it.