You're sending money thru intermediaries on SN (custodial zaps)
Revisit the central point of Bitcoin
"When will monero stop being a niche currency with real adoption outside of darknet markets?" All white markets are permissioned. Bitcoins entire value prop rests on being permissionless. Regulators can impose any arbitrary restriction they want on white markets up to, and including, banning Bitcoin transactions. Darknet markets are ironically the only "real" adoption. DNMs are a subset of Black markets AKA the only permissionless markets that are relevant to Bitcoins value prop.
If you're going to have your transactions permissioned anyway fiat is much better for that. At least everyone accepts fiat as payment.
DNMs are a subset of Black markets AKA the only permissionless markets that are relevant to Bitcoins value prop.
Afaik, most if not all DNMs use escrow which is not permissionless. DNMs regularly exit scam by allowing payments to go in but not out. So how exactly are DNMs pernssionless?
I'll give you a point about SN requiring permission but you're also missing some points which I don't have time or desire to explain. Maybe later.