Send money via routing number

I cannot send money to someone via Routing and account number. I don’t get the plaid thing. They clearly won’t give me their account password so i can send them money?!

I believe this is why apps like Cashapp and Zelle exist in the U.S

Plaid is for sending money to your own accounts at other banks. Generally speaking, it’s not a “thing” in the US to ask for someone’s bank details to send them money unless you’re a business. You’d either use a third party payment app like Venmo or CashApp, a fast payment service like Zelle or Popmoney if your bank supports it (Monzo doesn’t support either yet) or send them a paper check if they don’t want to use a payment app. Less often, some banks allow you to send someone a payment link where they can provide their bank details directly to your bank.