I've worked at a few credit unions, so some I know some ways of preventing check fraud! I'm in the USA so what I know only applies here.

1. Your bank/CU probably account has notes on it. At the places I've worked, you're supposed to leave a note for every transaction a customer does at the counter, in the drive thru or night deposit box, or over the phone. Due to the Bank Secrecy Act, if you deposit or withdrawal over $10k at any time, we have to fill out a document that goes to the government. If someone comes in with a check and mentions anything that sounds like they're being scammed, we're supposed to ask questions to help prevent someone from losing all their money. $10k+ in one day, and we're supposed to ask questions about the source of the funds or where it's going. (people can refuse to answer or be super vague, but it's still being documented and sent to the gov)
2. While I don't know of any legal services that let you use routing and account numbers without any verification, I do know that there are ways to get around it. Some ways are social engineering and phishing. A scammer calls their victim claiming to be from Venmo. The scammer will manipulate the victim into giving away their login information, and then the scammer attempts login. Still on the phone with the victim, they'll advise the victim they're going to get a text message with an authentication code. Now the scammer is past your secondary authentication and has access to whatever you have connected to your Venmo, and that was the most common kind of the ACH fraud I saw. This method applies to pretty much any money transferring service, though some apps definitely have updated security features since I was working at the CU.
3. When a person becomes a victim of some form of financial fraud, they're more likely to be victimized again. So when we as a financial institution find out the routing and account number of an account have been compromised, we have the member close their account. Remember our notes? I forgot to say that we can make immortal teller notes, and we'll make sure that every teller and phone rep that ever helps you for the rest of the money-eternity knows you got bamboozled out of $1000 by your tinder girlfriend after taking out a loan with your new wife, and tried to lie to us 6 different times over the course of 5 hours and 10+ phone calls before eventually admitting you gave your bank account login and ACH information to someone you've known for a week that you met online.
   ...So anyway, financial institutions are supposed to look out for you. If we know you've been scammed before, we'll do what we can to prevent it from happening again. We restrict certain kinds of transactions(like phone or online transactions, sometimes even drive-thru), block all cards and issue new ones, and sometimes close an account and make an entirely new one. If someone is well versed at check fraud, at some point that person's financial institution is going to catch and stop it. Once that bridge is burned, they have to start the whole process over. A well versed check fraudster will actually be spending more time tricking people out of their information, running the extended warranty scams and sus e-mails you hopefully don't open, than stealing your money. They have to act fast before an account gets closed.

Most people know these scams and can avoid them, but a lot of vulnerable people fall for it. Communication with someone who isn't the scammer is the best way to prevent it- whether that's family, friends, or your bank. Sorry this came out so long- there are a WHOLE lot more ways that fraud is prevented from my experience as a teller but it's 3am so I'll shut up!