I'm hoping it's them or Scotland. It's just such an underwhelming ability, like you said. Maybe if they scaled it so that it was +1 culture for each district in the city. A three district city would get +3 culture for the trade route, for example. Wouldn't be overpowered, but you can at least feel the bonuses. My personal wish is they could keep the +1 loyalty bonus as it is, but give the Dutch the ability to cancel trade routes, so that you could quickly re-route traders to help out, instead of having to keep traders on standby.
But you could make the case that Netherlands has a great civ Ability, UU, and UI so maybe that would be a bridge too far in giving them power. So I think Scotland would be a better candidate. Scotland just has a good civ Ability. Their UU and UI are so weak compared to others. And Robert's ability completely relies on declaring Wars of Liberation, which you may not even get to use in an entire game. Scotland could really use some help. An alt leader would be very welcome.