You played it really well, including (not) playing Lookout and Spice Merchant for coins at the right moments. The only thing I'd have done differently is to get a Highway before your first Merchant Guild because it cycles a bit more and is slightly more likely to get you to 5 the turn you play it, but that's a really minor thing.
There isn't necessarily anything wrong with finishing with so many tokens left. Buys were always going to be the limiting factor here. In a solitaire game you could choose to not get all the Highways, but in a 2p game you want them for denial: your T11 made it completely impossible for your opponent to ever win the game.
Remember that optimal play means maximizing your win chances, not winning as quickly or efficiently as possible. If on T9 you can choose between play A which gives you 99% chance of winning on T10, and play B which gives you 100% chance of winning somewhere before T20, B is the optimal choice. And if the percentages were equal,
both would be optimal, at least according to primitive game theory that doesn't account for Goko's instability and its penchant for inducing misclicks