Why does TSB "new" system from 2018 look same as the old one?

Section62

Alex9384 said:

Why would you build a brand new banking that looks like an old dull boring legacy banking?

You seem to discount the possibility TSB were aiming to look like "an old dull boring legacy bank".  It fitted with their strategy at the time - alongside making a big point of having lots of high street branches.

On the back of events in 2008/2009 there was a lot to be said for looking dull and boring. That still applied in 2018, and to some extent it still applies today.

Not everyone is a neophile.