OK, I work at Plaid and I feel like I have to jump in here -- while it's true that we've iterated on the Plaid Link UI over time and it hasn't always looked like it does now, you can see what the login screen currently looks like here: https://plaid.com/plaid-link/ and here: https://plaid.com/demo/
IMO it does clearly tell end users that they are connecting to Plaid.