People often say things like, "Satoshi got so much right"--but I think he didn't think through some things, or just assumed that the software would evolve as needed to compensate for scaling issues. Whatever he thought, I'm certain he didn't envision 8 billion people owning their own UTXOs since it would take something like 40 years worth of blocks for that single UTXO claim to process (and that's even with segwit)--and then what? No on-chain system scales by itself--that's the blockchain CAP theorem: Security, Scalability, Decentralization, you get 2/3 onchain, for the 3rd you need a layer 2. Satoshi made the decision that Decentralization and Security were paramount and that Scalability would come later. Some cryptos mistakenly think that Scaling should be one of the 2 on-chain pillars and that's why they will fail, because they sacrificed on-chain Decentralization or Security.