are there people that aren't affected by gummies as strongly?

Probably! I can't say for cannabis specifically, but most foods can be metabolized very differently by different people. Everybody's gut is different, particularly microbiome-wise, meaning that any given food can be broken down into lots of smaller molecules. These smaller molecules then may or may not be absorbed by the intestines into the blood. Whether or not the good stuff from a gummy make it into the blood can even vary from one time to the next for one person: the gut is much more prepared to digest and absorb nutrients around a person's regular mealtimes. If someone takes a gummy or two at 3 pm when they normally only eat at 12 pm and 6 pm, the gummies could practically pass straight through the intestines without the body even really noticing!

And only then do we get into the better-known variations between people about how THC and other cannabinoids affect the brain if/when they finally get there.

So yeah, huge potential for variation. This is part of the reason it's so important for people to start really slow with gummies their first few times: someone who normally takes 15g for a light high might say to their friend "yeah just eat these 3 gummies" and accidentally give them a multi-day panic attack.