I don’t think you understand what registering and being a FFL entails. There is nothing simple about it. First you go through a lengthy paperwork and BS process (https://www.atf.gov/firearms/apply-license). There are application and annual renewal fees. The ATF commonly performs inspections without announcement. It’s your responsibility that the person you are selling to folks out the 4473 completely & without errors. You are required to hold those forms for a period of 20 years.
Restricting people’s ability to sell their own personal property of firearms does indeed infringe upon people’s ability to keep & bear arms. You’re smart and can understand that.
If you were required to any of these things for any other constitutionally protected right, I suspect you would lose your shit. Because it is guns and you feel that it does not effect YOU directly, you are perfectly ok with the infringement.