My comment was more an invitation for Kaj to steelman his own point than an objection, but I see what you're getting at.

Key differences:

• 1: weirdness: A Boardgame night is extremely normal. Tons of normal people and nerds have variations on the concept. A Ritual night is very odd, and therefore automatically screens out outsiders.
• 1. Exclusionary: Indeed, the entire point of Rituals is to draw a line between them and us. This is off-putting to anyone who does not want to put themselves into the "us". A new person can happily join in and enjoy the familiarity of playing boardgames and not feel like they're being indoctrinated. They can get to know and bond with strangers over something familar. This is basically what Said earlier in this thread.
• 1. Room for individuality/nonparticipation: Boardgame night does not consist of the same thing each time. Maybe some nights we play Resistance, maybe other nights we play Dominion, and maybe different subsets of boardgame night play different games. A ritual not only makes everyone do the same thing, it makes them do it all at once. No one really cares if you overhear "I've got wood for sheep!" while you're playing Ascension, or just having a conversation, but it would certainly ruin the mood of a ritual. The only polite responses to Ritual are participation, silence, or leaving.

• There's some more I feel I can say on this but I can't yet articulate it appropriately. It has to do with seriousness and how much I value banter and puncturing self-importance.