The average ICE car gets around 13 miles per litre.
Say petrol is at its current price, around 137p/L. 23p of that is VAT, 53p is fuel duty. So you're paying 5.8p in tax per mile.
3p per mile for EV drivers starts to look pretty reasonable.
There is a lot of unfairness built in with EVs unless we get major structural change (such as the ability to access your household electricity account from a street charger near your house, for example - the real incentive for EVs comes from being able to mainly charge using flexible EV tariffs, and that will only increase as more variable tariffs come onto the market.) But "you might have to pay some tax based on how much you drive, same as ICE drivers" is unlikely to be one of the unfair things.
It was always going to happen once takeup got past a tipping point.