Don't worry. I feel like I'm a shit mum at these events all the time. I always try to attend, but I just find them all so boring and tedious. I feel like I'm the only one not enjoying it. All mine are at different Key Stages, so I often have to attend the same event two or three times, depending on how they split the year groups.
I make the effort for my children and smile and wave, and tell them how well they did afterwards, but there's only so many times you can watch kids trying and failing to throw bean bags into hoops.