Being serious for a bit, this goes without saying. Like with everything in life, balance remains a key quality.
Just like with the white blood cell analogy. Too little any virus can pretty much destroy you, and too much...you get leukemia.
Too little water, you suffer dehydration, too much, you get water intoxication.
Same balance goes for a fandom - its completely fine and to accept newcomers who want to be part of a fandom because the newcomers came for what’s already there. Otherwise the fandom will fizzle and disappear because no one is left to keep it alive.
What is NOT fine, is when people who never cared for the fandom or even overtly hate it. Trying to force their way in to change it from the inside whether to satisfy their ego or to spite the ones already in it, hence reason why Gatekeeping exists and should continue to exist.
The debate should instead be "how much gatekeeping?" Doesn’t matter if its Vtubers, Video games, Anime etc.