Disciplined monthly equity investing

Do any of you commit a regularly monthly amount to investment in equity instruments such as Vanguard total index fund VTSMX? This is supposed to be the most failproof method to create long term wealth. If so, I'd be curious to know how difficult or easy this process is ? I have used Ameritrade and even though you can setup recurring debits from the bank, you can't automatically buy every month. There are these robo advisor companies but even they don't have this feature of automated regular buys. Like I can't just submit a trade like 'Buy $500 VTSMX every month' and the broker does the rest. Am I missing something ?