I looked it up and it can indeed go up to 13.5% inclination but they can only run powered cars, no attached wagons. That reduces capacity.

I don't want to shit on trams. I don't like this bus vs tram bashing in either direction. I'll happily take either improvement over a sea of cars...

I don't quite remember what they're called but in the UK there's both old mining trains and old cliff trains/trolleys that use toothed wheels and toothed tracks on the hill portions to go up/down hill with little issue, obviously it's only safe for some gradient, but still with the right gearing it would be of possible

Don't they use rubber tired trams, aka guided buses?