The throughput of possible UTXOs may not have changed but the throughput of transactions with non-trivial scripts has. Now we can construct a transaction with a 2 of 3 multisig and spend it without including anything in the scriptsig. Reducing transactions with complex scripts to an anyone-can-spend transaction with a small scriptpubkey does increase the transaction throughput for the most common use-case for example, which is just paying to a public key hash (https://dune.com/murchandamus/bitcoins-utxo-set)