The Omicron variant may pose more of a risk (or less, depending on the science) but Covid was always going to be circulating and gigs a risk, so I can’t see how the decision has changed much from when you accepted the gig.
The prevailing political view seems to be that life can continue as close to normal as it can. Again, you either trust the Government or not (this isn’t the place for that discussion).
You have no moral duty to those people in the crowd, but you do to your family and friends.
Personally, I’d do all I can to limit contact at the gig, follow the rules and just get on with it. And try and enjoy it if you can!