You look at your DE all day and your distro holds everything together. Op didn’t say distro is unimportant and I agree it makes sense for new users to look at images and videos of different desktops first, maybe try a live cd, and then choosing the backend that suits their willingness to interact with.
If your electricity and time are cheap, you want to learn and your pc-system is your playground not a productivity tool, Gentoo is a valid option. In this case, your choice of DE impacts your compile time massively and knowing alternatives beforehand gives you options.