He's right, gamers shouldn't make games. Software developers, artists, and animators should. 343 and the modern Halos are what happens when a bunch of people who said "I WANT TO WORK FOR VIDEO GAMES WHEN I GROW UP!" actually get what they want. That company is staffed entirely by industry newfags who are just barely old enough to have gone into their profession BECAUSE they played Halo when they were in highschool, and wanted to "make Halo" when they got out of college. They got their wish, and Halo 4, 5, and MCC have been trash.
Gamers don't have original ideas, they just want "an open-world X mixed with Y plus GIMMICK." It's like if someone who writes has a favorite author, they unwittingly mimic their writing style until called out on it.