ACH has had same day payments since 2016. If your bank takes until "next morning" then that's your bank's problem, not ACH's.

https://www.nacha.org/resource-landing/same-day-ach-resource...

That said, FedNow is still an improvement over ACH. ACH is fundamentally batch-based processing, they just run the batch multiple times per day now. And all the batch times are East Coast biased, so people on the West Coast get worse service.