We're going back to square one with the 'empties my account' comment. You can mitigate that but changing your password pre/post transaction so the login you use is one-time. It is inconvenient, but worth it if you do not trust the vendor and want to avoid credit card fees.
If you are concerned about them getting your past transactions, you can always create a new account, or even a new bank account just for use for these type of situations. There's still some transaction history, but not nearly as much as a day to day account. I do think there's a lot of value in Plaids services but having said that, it is all a work around due to the abysmal financial infrastructure of the USA and lack of real time payments. Plaid services and requiring bank logins to do transactions does seem a bit whack, but again US payment system is even whacker.
Given that for other ACH transfers I'm able to just hand out my routing+account number and that's all that is necessary to complete the transfer. The fact that companies are training people to input their bank username/password on other websites is completely insane, even if some might know to change it afterwards. If a scammy website did this, I'm willing to bet you money they'll change that password faster than you ever could.