I'm sure Starling will impose a cap at some point and then it will be on to the next one.
I'd rather fewer orgs have my details, so I'm more inclined to just take out a wodge of currency before I go anywhere and then use the card/cash as appropriate.
A lot of the other modern cards (Tandem, Revolut, Monzo, etc) use the same rate.
The only issue is cash withdrawals where, as mentioned above, when they get more popular a limit is imposed for ATM withdrawals with a fee after that.
I'm sure Starling will impose a cap at some point and then it will be on to the next one.