The entirety of how silly the metal scene can be can be summed up by Devin Townsend's Pünky Brüster in their album Cooked on Phonics. One of Townsend's more underrated albums, and honestly, ironically enough, one of the best punk albums of the 90's.
There are a lot of elements to a musical piece, regardless of genre. So if someone says not metal enough, ask them exactly why. Maybe they’re right, or maybe they’re wrong. But calling them gatekeepers without discussing composition, arrangement, thematic elements etc. doesn’t help maintain genre quality in the long run. If they’re using 1 or 2 favorite bands as a barometer, then that’s just stupid.
I often asked them. Things often brought up were use of guitar effects, no guitar solos, wrong type of vocals (with rapping was the most criticized back in my days, nowadays it's harsh vs. clean vocals mainly), being popular, making more money from merchs/endorsements than record sales, and my personal favorite: not understanding music theory and how music is played so much you think only losers play power chords in the genre dominated by power chords.
I just wrote a number there, but a pretty big former friend of mine started to go really bad at that point. He started to post fashy stuff on his timeline (especially LoTT), deleted it before the Hogwarts Legacy drama (likely to claim he was made fascist by the impending drama), he suddenly became a big fan of Silvervale (he previously hated VShojo and their talents), also became a fan of Pipkin Pippa. However, he somehow realized they weren't actual nazis (both are... complicated...), so he entered an interesting arc, where he basically gradually stops liking every geeky stuff he did in the past, because he realized they're "woke".