Everybody has different sized ears, even from left and right ears.
Finding a universal fit is an issue.
I don't like the OEM APP cheap silicone tips in that it doesn't fit well and don't provide a proper seal in the ear. You need that seal for the sound isolation and proper fit.
Third party tips are a hit and miss.
Anyone who's owned/used in-ear/monitor earphones (i.e. Westone & Shure) know that the eartips are crucial. There are lots of foam ear tips including larger sizes. Squeeze the foam tips then place it into your ears. The foams will expand to fit. It's not difficult finding good Foam ear tips!
Unfortunately, lots of people Never had in-ear earphones so complain about the Discomfort of having something in their ears. It takes time to get used to it!
No one ever mentions that partially the case design is also at fault. The tips have to fit a certain size or the APPs won't fit into the case. The case won't allow a larger or round tips to be used as the APP case won't allow it!
As long as you get the best tip available then angle the APP to fit into your ear with a good seal, you're good!