The smoothly curved, narrow mountain chains look definitely magical rather than natural, especially the sharp point where the three of them join at 90 degrees (tectonic plates almost always join at 120 degree angles). If this is your intention that's cool.

I love the colours! Very convincing colour choices.

That long river kind of stands out to me as well. Having the elevation go so smoothly from one side of the continent all the way to the other looks really weird.

The rivers on the north side of the mountain range look more wiggly than one might expect for such a steep environment -- wiggly rivers are more common on very shallow slopes, and this looks like a fairly steep and tectonically active area, so I'd expect straighter rivers with deeper canyons than you seem to have here. The rivers coming out of the Sierra Nevada and joining the Sacramento/San Joaquin drainage are a good example of what I'd expect to see here, although there's no second mountain range for them to go through so they wouldn't necessarily converge like that before hitting the ocean.

And if the eastern end of that continent is so green, shouldn't there be at least one good-sized river going through there?