Most of the online wallet nowadays requires a confirmation before proceeding on the transaction. Not only in the bitcoin wallet but some local wallets have also a confirmation feature to avoid mistake transactions. Undo feature might be helpful but it'll lessen the discipline of checking the correct information on every transactions.
Even now that there is no undo button for transactions, a lot of people are still being scammed because they sent their money to a scammer or they sent to a wrong address.
Sending to wrong address doesn't means you got scammed, it's stupidity. That's why it's better to request for both qr code and wallet address of sender when sending a transaction. All you need is two devices, a PC and a mobile phone that you're going to send the coin from.
That's why we shouldn't rush things and do the transactions carefully to avoid problems. There are many of scammers in the digital world, always hesitate to transact with someone we doesn't know personally.